Edexcel Triple Science: Physics — Recall & Retrieval

1.1 Recall and use the SI unit for physical quantities, as listed in Appendix 3

1.

What is the SI unit for length?

The metre (m).

2.

What is the SI unit for mass?

The kilogram (kg).

3.

What is the SI unit for time?

The second (s).

4.

What is the SI unit for electric current?

The ampere (A).

5.

What is the SI unit for temperature?

The kelvin (K).

6.

What is the SI unit for energy?

The joule (J).

1.2 Recall and use multiples and sub-multiples of units, including giga (G), mega (M), kilo (k), centi (c), milli (m), micro (μ) and nano (n)

1.

What multiplier does the prefix giga (G) represent?

10⁹.

2.

What multiplier does the prefix mega (M) represent?

10⁶.

3.

What multiplier does the prefix kilo (k) represent?

10³.

4.

What multiplier does the prefix centi (c) represent?

10⁻².

5.

What multiplier does the prefix milli (m) represent?

10⁻³.

6.

What multipliers do the prefixes micro (μ) and nano (n) represent?

Micro (μ) represents 10⁻⁶, and nano (n) represents 10⁻⁹.

1.3 Be able to convert between different units, including hours to seconds

1.

How many seconds are there in one minute?

60 seconds.

2.

How many seconds are there in one hour?

3600 seconds.

3.

How would you convert a measurement in hours into seconds?

Multiply the number of hours by 3600.

4.

Convert 2.5 hours into seconds.

Time = 2.5 × 3600 = 9000 s.

5.

Convert 3600 seconds into hours.

Time = 3600 ÷ 3600 = 1 hour.

6.

Convert 5 kilometres into metres.

Length = 5 × 1000 = 5000 m.

1.4 Use significant figures and standard form where appropriate

1.

What is meant by significant figures?

The digits in a number that contribute to its precision, including all certain digits and the first uncertain digit.

2.

How many significant figures does 0.00450 have?

3 significant figures: 4, 5 and 0.

3.

How should 7.846 be rounded to three significant figures?

7.85.

4.

What is standard form?

A way of expressing a number as a × 10ⁿ, where 1 ≤ a < 10 and n is an integer.

5.

Express 450,000 in standard form.

4.5 × 10⁵.

6.

Express 0.000032 in standard form.

3.2 × 10⁻⁵.

2.1 Explain that a scalar quantity has magnitude (size) but no specific direction

1.

What is a scalar quantity?

A physical quantity that has magnitude only, with no specific direction.

2.

What does the magnitude of a physical quantity describe?

The size or numerical value of the quantity.

3.

Does a scalar quantity have a specific direction?

No.

4.

Is distance a scalar quantity?

Yes, because it has magnitude but no direction.

5.

Is speed a scalar quantity?

Yes, because it has magnitude but no direction.

6.

What is the defining feature of a scalar quantity?

That it has magnitude but no direction.

2.2 Explain that a vector quantity has both magnitude (size) and a specific direction

1.

What is a vector quantity?

A physical quantity that has both magnitude and a specific direction.

2.

What two properties does a vector quantity have?

Magnitude and direction.

3.

Does a vector quantity have a specific direction?

Yes.

4.

Is velocity a vector quantity?

Yes.

5.

Is force a vector quantity?

Yes.

6.

What is the defining feature of a vector quantity?

That it has both magnitude and direction.

2.3 Explain the difference between vector and scalar quantities

1.

What is the difference between a scalar and a vector quantity?

A scalar has magnitude only, whereas a vector has magnitude and direction.

2.

Which type of quantity has magnitude but no specific direction?

A scalar quantity.

3.

Which type of quantity has both magnitude and direction?

A vector quantity.

4.

Why is speed a scalar quantity?

Because it describes how fast an object moves without specifying a direction.

5.

Why is velocity a vector quantity?

Because it describes speed in a stated direction.

6.

What additional information is required for a vector quantity compared with a scalar quantity?

Directional information in addition to its magnitude.

2.4 Recall vector and scalar quantities, including: a displacement/distance b velocity/speed c acceleration d force e weight/mass f momentum g energy

1.

Which is a vector quantity: displacement or distance?

Displacement is a vector quantity; distance is a scalar quantity.

2.

Which is a vector quantity: velocity or speed?

Velocity is a vector quantity; speed is a scalar quantity.

3.

Is acceleration a scalar or vector quantity?

A vector quantity.

4.

Are force, weight and momentum scalar or vector quantities?

Vector quantities.

5.

Is mass a scalar or vector quantity?

A scalar quantity.

6.

Is energy a scalar or vector quantity?

A scalar quantity.

2.5 Recall that velocity is speed in a stated direction

1.

What is velocity?

Speed in a stated direction.

2.

What additional information does velocity provide compared with speed?

The direction of motion.

3.

Why is velocity a vector quantity?

Because it has both magnitude and direction.

4.

What is the difference between speed and velocity?

Speed gives magnitude only, whereas velocity gives magnitude and direction.

5.

Can two objects have the same speed but different velocities?

Yes, if they are moving in different directions.

6.

What happens to an object's velocity when its direction changes but its speed remains constant?

Its velocity changes, because its direction has changed.

2.6 Recall and use the equations: a (average) speed (metre per second, m/s) = distance (metre, m) ÷ time (s) b distance travelled (metre, m) = average speed (metre per second, m/s) × time (s)

1.

What is the equation for average speed?

Average speed = distance ÷ time.

2.

What is the SI unit for speed?

Metre per second (m/s).

3.

What is the equation for distance travelled using average speed and time?

Distance = average speed × time.

4.

What is the average speed of an object that travels 150 m in 10 s?

speed = 150 ÷ 10 = 15 m/s.

5.

How far does an object travel at 20 m/s for 5 s?

distance = 20 × 5 = 100 m.

6.

How can the speed equation be rearranged to calculate time?

time = distance ÷ speed.

2.7 Analyse distance/time graphs including determination of speed from the gradient

1.

What does the gradient of a distance/time graph represent?

The speed.

2.

How is speed calculated from a distance/time graph?

speed = change in distance ÷ change in time.

3.

What does a horizontal line on a distance/time graph represent?

An object that is stationary.

4.

What does a straight line with a constant positive gradient represent?

Constant speed.

5.

What does a steeper gradient on a distance/time graph indicate?

A greater speed.

6.

What does a changing gradient on a distance/time graph indicate?

That the object's speed is changing.

2.8 Recall and use the equation: acceleration (metre per second squared, m/s²) = change in velocity (metre per second, m/s) ÷ time taken (second, s) (v − u) ÷ t = a

1.

What is the equation for acceleration?

a = (v − u) ÷ t.

2.

What is the SI unit for acceleration?

Metres per second squared (m/s²).

3.

What does u represent in the equation a = (v − u) ÷ t?

The initial velocity.

4.

What does v represent in the equation a = (v − u) ÷ t?

The final velocity.

5.

What is the acceleration when velocity changes by 20 m/s in 5 s?

a = 20 ÷ 5 = 4 m/s².

6.

What does a negative acceleration indicate about an object's velocity?

That its velocity is decreasing in the chosen positive direction.

2.9 Use the equation: (final velocity)² − (initial velocity)² = 2 × acceleration × distance, v² − u² = 2 × a × x

1.

What equation relates final velocity, initial velocity, acceleration and distance?

v² − u² = 2ax.

2.

What does v represent in v² − u² = 2ax?

The final velocity.

3.

What does u represent in v² − u² = 2ax?

The initial velocity.

4.

What does a represent in v² − u² = 2ax?

The acceleration.

5.

What does x represent in v² − u² = 2ax?

The distance travelled.

6.

What quantity can be calculated using v² − u² = 2ax when the other three quantities are known?

Any one of final velocity, initial velocity, acceleration or distance.

2.10 Analyse velocity/time graphs to: a compare acceleration from gradients qualitatively b calculate the acceleration from the gradient (for uniform acceleration only) c determine the distance travelled using the area between the graph line and the time axis (for uniform acceleration only)

1.

What does the gradient of a velocity/time graph represent?

Acceleration.

2.

How can the acceleration of two objects be compared using their velocity/time graph gradients?

The object with the steeper gradient has the greater magnitude of acceleration.

3.

How is acceleration calculated from the gradient of a velocity/time graph?

acceleration = change in velocity ÷ change in time.

4.

What does the area between a velocity/time graph and the time axis represent?

The distance travelled, when velocity is positive.

5.

How can the distance travelled be determined from a velocity/time graph?

By calculating the area under the graph.

6.

What does a horizontal line on a velocity/time graph represent?

Constant velocity, so the acceleration is zero.

2.11 Describe a range of laboratory methods for determining the speeds of objects such as the use of light gates

1.

What is a light gate used to measure in a motion experiment?

The time taken for an object, or a card of known length, to pass through it.

2.

How can light gates be used to determine the speed of an object?

By measuring the time taken for a known length to pass through the gate and using speed = distance ÷ time.

3.

What measurements are needed to calculate speed using a light gate?

The length of the object or card and the time taken.

4.

Why can a light gate provide a more precise measurement of time than a stopwatch operated by a person?

It measures time electronically, reducing human reaction-time errors.

5.

What other laboratory method could be used to determine the speed of a moving object?

Using a stopwatch, measuring the distance travelled and the time taken.

6.

How can the length of an object passing through a light gate be used to calculate its speed?

speed = length of object ÷ time taken.

2.12 Recall some typical speeds encountered in everyday experience for wind and sound, and for walking, running, cycling and other transportation systems

1.

What is a typical speed for a person walking?

About 1.5 m/s.

2.

What is a typical speed for a person running?

About 3 m/s.

3.

What is a typical speed for a person cycling?

About 6 m/s.

4.

What is the approximate speed of sound in air?

340 m/s.

5.

What is a typical speed for wind?

About 10 m/s, although this varies considerably.

6.

How do typical transportation speeds compare with walking and running speeds?

They are generally faster, with cars commonly travelling around 13–30 m/s.

2.13 Recall that the acceleration, g, in free fall is 10 m/s² and be able to estimate the magnitudes of everyday accelerations

1.

What is the acceleration due to gravity, g, near Earth's surface?

10 m/s².

2.

What is the SI unit for gravitational acceleration?

m/s².

3.

What does an acceleration of 10 m/s² mean for a freely falling object?

Its velocity increases by 10 m/s every second, neglecting air resistance.

4.

In which direction does gravitational acceleration act near Earth's surface?

Downwards, towards the centre of the Earth.

5.

How can the magnitude of an everyday acceleration be estimated?

a = change in velocity ÷ time.

6.

How does gravitational acceleration compare with typical accelerations in everyday motion?

It is much larger than many ordinary accelerations, such as walking or cycling.

2.14 Recall Newton's first law and use it in the following situations: a where the resultant force on a body is zero, i.e. the body is moving at a constant velocity or is at rest b where the resultant force is not zero, i.e. the speed and/or direction of the body change(s)

1.

What does Newton's first law state?

An object remains at rest or moves with constant velocity unless acted upon by a resultant external force.

2.

What happens to an object when the resultant force acting on it is zero?

It remains at rest or continues moving at constant velocity.

3.

What is the velocity of an object moving at constant velocity when the resultant force is zero?

It remains constant, including both speed and direction.

4.

What happens to an object's motion when the resultant force is not zero?

Its velocity changes.

5.

Can an object be moving when the resultant force acting on it is zero?

Yes.

6.

What changes in motion can result from a non-zero resultant force?

A change in speed, direction, or both.

2.15 Recall and use Newton's second law as: force (newton, N) = mass (kilogram, kg) × acceleration (metre per second squared, m/s²) F = m × a

1.

What is Newton's second law equation?

F = m × a.

2.

What is the SI unit of force?

The newton (N).

3.

What happens to acceleration if force increases while mass remains constant?

Acceleration increases in direct proportion to the force.

4.

What happens to acceleration if mass increases while force remains constant?

Acceleration decreases.

5.

What force is needed to accelerate a 5 kg mass at 4 m/s²?

F = 5 × 4 = 20 N.

6.

What acceleration is produced by a 20 N force acting on a 4 kg mass?

a = 20 ÷ 4 = 5 m/s².

2.16 Define weight, recall and use the equation: weight (newton, N) = mass (kilogram, kg) × gravitational field strength (newton per kilogram, N/kg) W = m × g

1.

What is weight?

The force acting on an object due to gravity.

2.

What is the equation relating weight, mass and gravitational field strength?

W = m × g.

3.

What is the SI unit for weight?

The newton (N).

4.

What is the SI unit for gravitational field strength?

Newtons per kilogram (N/kg).

5.

What is the weight of a 10 kg object in a gravitational field of 10 N/kg?

W = 10 × 10 = 100 N.

6.

How does an object's weight change if its mass doubles in the same gravitational field?

Its weight also doubles.

2.17 Describe how weight is measured

1.

What instrument can be used to measure weight?

A spring balance (newton meter).

2.

What physical quantity does a spring balance measure?

Force, including the force due to gravity.

3.

What unit is normally used when measuring weight?

Newtons (N).

4.

How does a spring balance indicate the weight of an object?

The object's weight stretches the spring, and the scale reading gives the force.

5.

Why is a spring balance suitable for measuring weight?

Because the extension of its spring is related to the force applied.

6.

How could the weight of an object be measured experimentally?

Attach it to a spring balance, allow it to hang at rest, and read the force in newtons.

2.18 Describe the relationship between the weight of a body and the gravitational field strength

1.

What is the relationship between weight and gravitational field strength for a fixed mass?

Weight is directly proportional to gravitational field strength.

2.

What happens to weight when gravitational field strength increases?

Weight increases.

3.

What happens to weight when gravitational field strength decreases?

Weight decreases.

4.

How does gravitational field strength affect the weight of an object on different planets?

An object weighs more where the gravitational field strength is greater and less where it is weaker.

5.

Why does an object's mass remain constant when its gravitational field changes?

Mass is the amount of matter in an object, whereas weight depends on the gravitational field.

6.

Which equation shows the relationship between weight, mass and gravitational field strength?

W = m × g.

2.19 Core Practical: Investigate the relationship between force, mass and acceleration by varying the masses added to trolleys

1.

What relationship between force, mass and acceleration is investigated in this practical?

F = m × a.

2.

What apparatus can be used to investigate force, mass and acceleration?

A trolley, masses, pulley, string, light gates or motion sensor, and a force-producing mass or force sensor.

3.

What variable can be changed by adding masses to a trolley?

The mass of the trolley system.

4.

What measurements are needed to determine acceleration?

Measurements of velocity and time, or equivalent motion data.

5.

What variable should be controlled when investigating the effect of force on acceleration?

The total mass of the system should be kept constant.

6.

What relationship between force and acceleration is expected when mass is kept constant?

Force and acceleration are directly proportional.

2.20 Explain that an object moving in a circular orbit at constant speed has a changing velocity (qualitative only)

1.

Why does an object moving in a circle at constant speed have changing velocity?

Because its direction of motion continuously changes.

2.

What component of velocity changes during circular motion at constant speed?

The direction component.

3.

Is velocity constant when an object travels around a circle at constant speed?

No, because its direction changes.

4.

Why can velocity change even when speed remains constant?

Because velocity includes direction, whereas speed only describes magnitude.

5.

What happens to the direction of velocity during circular motion?

It changes continuously as the object moves around the circle.

6.

Why is circular motion considered accelerated motion even when speed is constant?

Because acceleration is a change in velocity, and velocity changes even when speed is constant.

2.21 Explain that for motion in a circle there must be a resultant force known as a centripetal force that acts towards the centre of the circle

1.

What is centripetal force?

The resultant force directed towards the centre of a circular path.

2.

In which direction does centripetal force act?

Towards the centre of the circle.

3.

Why is a resultant force required for circular motion?

Because the object's velocity is continually changing direction.

4.

What effect does centripetal force have on the direction of velocity?

It continually changes the direction of the object's velocity.

5.

What would happen to an object moving in a circle if the centripetal force disappeared?

It would move off in a straight line tangential to the circle.

6.

Why is centripetal force directed towards the centre of the circle?

Because it provides the inward acceleration needed to continuously change the direction of motion.

2.22 Explain that inertial mass is a measure of how difficult it is to change the velocity of an object (including from rest) and know that it is defined as the ratio of force over acceleration

1.

What is inertial mass?

A measure of how difficult it is to change an object's velocity.

2.

What does inertial mass measure?

An object's resistance to acceleration.

3.

How does greater inertial mass affect the difficulty of changing an object's velocity?

It makes it more difficult to change.

4.

How is inertial mass defined using force and acceleration?

As the ratio of force to acceleration.

5.

What is the equation for inertial mass?

m = F ÷ a.

6.

How can inertial mass be determined experimentally using measurements of force and acceleration?

Apply a known force, measure the acceleration, and calculate m = F ÷ a.

2.23 Recall and apply Newton's third law both to equilibrium situations and to collision interactions and relate it to the conservation of momentum in collisions

1.

What does Newton's third law state?

When two objects interact, they exert equal and opposite forces on each other.

2.

What are the key features of a Newton's third-law pair of forces?

Equal in magnitude, opposite in direction, act on different objects, and are the same type of force.

3.

How does Newton's third law apply to objects in equilibrium?

Forces can balance to give a zero resultant force, while interaction forces on other objects remain equal and opposite.

4.

How does Newton's third law apply when two objects collide?

Each object exerts an equal and opposite force on the other.

5.

What happens to total momentum before and after an isolated collision?

It remains the same.

6.

How is Newton's third law related to conservation of momentum in collisions?

Equal and opposite interaction forces produce equal and opposite changes in momentum, so total momentum is conserved.

2.24 Define momentum, recall and use the equation: momentum (kilogram metre per second, kg m/s) = mass (kilogram, kg) × velocity (metre per second, m/s) p = m × v

1.

What is momentum?

The product of an object's mass and velocity.

2.

What is the equation for momentum?

p = m × v.

3.

What is the SI unit for momentum?

Kilogram metre per second (kg m/s).

4.

What happens to momentum if mass doubles while velocity remains constant?

Momentum doubles.

5.

What happens to momentum if velocity doubles while mass remains constant?

Momentum doubles.

6.

What is the momentum of a 5 kg object travelling at 4 m/s?

p = 5 × 4 = 20 kg m/s.

2.25 Describe examples of momentum in collisions

1.

What happens to the momentum of objects involved in a collision?

Objects can transfer momentum between each other.

2.

What is meant by conservation of momentum in a collision?

Total momentum before a collision equals total momentum after, provided no external resultant force acts.

3.

How can momentum be transferred between objects during a collision?

Through the forces the objects exert on each other.

4.

What happens to total momentum before and after an isolated collision?

It remains constant.

5.

How can the motion of two colliding objects demonstrate conservation of momentum?

A moving trolley colliding with a stationary trolley transfers momentum, so combined total momentum stays the same.

6.

Why is momentum important when analysing vehicle collisions?

It helps determine how vehicles' velocities change and the forces involved.

2.26 Use Newton's second law as: force (newton, N) = change in momentum (kilogram metre per second, kg m/s) ÷ time (second, s) (mv − mu) ÷ t = F

1.

How can Newton's second law be expressed in terms of change in momentum?

Force = rate of change of momentum.

2.

What is the equation relating force, change in momentum and time?

F = (mv − mu) ÷ t.

3.

What does mv − mu represent?

The change in momentum.

4.

What happens to force for a fixed change in momentum if the time taken increases?

The force decreases.

5.

What force acts when momentum changes by 60 kg m/s in 3 s?

F = 60 ÷ 3 = 20 N.

6.

What is the SI unit of force when calculated using change in momentum and time?

The newton (N).

2.27 Explain methods of measuring human reaction times and recall typical results

1.

What is meant by human reaction time?

The time taken between a stimulus being received and the resulting response being made.

2.

How can a ruler-drop experiment be used to measure reaction time?

One person drops a ruler without warning and the other catches it; the fall distance is converted to a reaction time.

3.

What measurement is taken in a ruler-drop reaction-time experiment?

The distance fallen by the ruler before it is caught.

4.

How can a computer-based test measure human reaction time?

It presents a stimulus and measures the time until the person responds, such as pressing a key.

5.

What factors can affect a person's reaction time?

Tiredness, concentration, distractions, drugs, alcohol and individual differences.

6.

What is a typical order of magnitude for human reaction time?

About 0.1–0.3 s.

2.28 Recall that the stopping distance of a vehicle is made up of the sum of the thinking distance and the braking distance

1.

What is stopping distance?

The total distance travelled by a vehicle from identifying a hazard until it stops.

2.

What two distances make up the stopping distance of a vehicle?

Thinking distance and braking distance.

3.

What is thinking distance?

The distance travelled during the driver's reaction time.

4.

What is braking distance?

The distance travelled after the brakes are applied until the vehicle stops.

5.

How is stopping distance calculated from thinking distance and braking distance?

Stopping distance = thinking distance + braking distance.

6.

Why does a vehicle continue travelling during the driver's reaction time?

Because the driver has not yet responded by applying the brakes.

2.29 Explain that the stopping distance of a vehicle is affected by a range of factors including: a the mass of the vehicle b the speed of the vehicle c the driver's reaction time d the state of the vehicle's brakes e the state of the road f the amount of friction between the tyre and the road surface

1.

How does the mass of a vehicle affect its stopping distance?

A greater mass generally increases braking force needed and increases braking distance.

2.

How does the speed of a vehicle affect its stopping distance?

Increasing speed increases stopping distance; braking distance increases approximately with speed squared.

3.

How does a driver's reaction time affect stopping distance?

A longer reaction time increases thinking distance and therefore stopping distance.

4.

How can the condition of a vehicle's brakes affect stopping distance?

Worn or poorly functioning brakes can increase braking distance.

5.

How can the condition of the road affect stopping distance?

Wet, icy or poor road conditions can reduce grip and increase braking distance.

6.

How does friction between the tyres and road surface affect stopping distance?

Greater friction increases available braking force and reduces braking distance.

2.30 Describe the factors affecting a driver's reaction time including drugs and distractions

1.

What is meant by a driver's reaction time?

The time between recognising a hazard and beginning the appropriate response.

2.

How can tiredness affect a driver's reaction time?

It generally increases reaction time.

3.

How can distractions affect a driver's reaction time?

They can increase reaction time by reducing attention to the road.

4.

How can drugs affect a driver's reaction time?

They can alter alertness, concentration and coordination, potentially increasing reaction time.

5.

Why does an increased reaction time increase thinking distance?

The vehicle travels for longer before braking begins.

6.

Why can distractions while driving increase the risk of a collision?

They can delay recognition of hazards and the driver's response.

2.31 Explain the dangers caused by large decelerations and estimate the forces involved in typical situations on a public road

1.

What is meant by a large deceleration?

A large decrease in velocity in a short period of time.

2.

Why can large decelerations be dangerous to vehicle occupants?

They produce large forces on vehicle occupants.

3.

How does deceleration affect the force experienced by an object?

For a given mass, greater deceleration produces a greater force.

4.

How can Newton's second law be used to estimate the force during rapid deceleration?

F = m × a, e.g. for a 60 kg person decelerating at 10 m/s², F = 600 N.

5.

Why do vehicle safety features aim to reduce the deceleration experienced by passengers?

They increase the time over which passengers are brought to rest, reducing the force for a given change in momentum.

6.

What quantities are needed to estimate the force acting during a vehicle's deceleration?

The mass and acceleration (or deceleration), or change in momentum and time.

2.32P Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds

1.

What two components make up a vehicle's total stopping distance?

Thinking distance and braking distance.

2.

How does thinking distance change as vehicle speed increases if reaction time is constant?

It increases directly with speed.

3.

How does braking distance change as vehicle speed increases?

It generally increases approximately with the square of speed.

4.

Why does stopping distance increase significantly at higher speeds?

Because braking distance increases approximately with speed squared.

5.

How can stopping-distance data be used to estimate stopping distance at different speeds?

By comparing distances at known speeds and estimating values between them.

6.

What factors should be considered when estimating the stopping distance of a road vehicle in an emergency?

Vehicle speed, driver reaction time, vehicle mass, brake condition, road condition and tyre-road friction.

2.33P Carry out calculations on work done to show the dependence of braking distance for a vehicle on initial velocity squared (work done to bring a vehicle to rest equals its initial kinetic energy)

1.

What type of energy does a moving vehicle have because of its motion?

Kinetic energy.

2.

How does a vehicle's kinetic energy depend on its initial velocity?

It depends on the square of the velocity: E = ½mv².

3.

What happens to the kinetic energy when a vehicle's initial velocity is doubled?

It quadruples, since E = ½m(2v)² = 4(½mv²).

4.

How is the work done to bring a vehicle to rest related to its initial kinetic energy?

Work done equals the initial kinetic energy.

5.

How does braking distance depend on the initial velocity squared?

Since work done W = F × d and kinetic energy is proportional to v², braking distance is also proportional to v².

6.

Why does a vehicle travelling at a higher initial velocity require a greater braking distance?

It has more kinetic energy, so more work must be done by the brakes to bring it to rest.

3.1 Recall and use the equation to calculate the change in gravitational PE when an object is raised above the ground: change in gravitational potential energy (joule, J) = mass (kilogram, kg) × gravitational field strength (newton per kilogram, N/kg) × change in vertical height (metre, m) ΔGPE = m × g × Δh

1.

What is the equation for calculating a change in gravitational potential energy?

ΔGPE = m × g × Δh.

2.

What are the units of gravitational potential energy, mass, gravitational field strength and height?

Joules (J), kilograms (kg), newtons per kilogram (N/kg) and metres (m).

3.

A 5 kg object is raised by 4 m where g = 10 N/kg. What is its increase in gravitational potential energy?

ΔGPE = 5 × 10 × 4 = 200 J.

4.

A 20 kg object gains 600 J of gravitational potential energy when raised through 3 m. What is the gravitational field strength?

g = 600 ÷ (20 × 3) = 10 N/kg.

5.

An object gains 1,500 J of gravitational potential energy when raised 5 m in a gravitational field of 10 N/kg. What is its mass?

m = 1500 ÷ (10 × 5) = 30 kg.

6.

A 2 kg object is raised through 8 m where g = 10 N/kg. What is its change in gravitational potential energy?

ΔGPE = 2 × 10 × 8 = 160 J.

3.2 Recall and use the equation to calculate the amounts of energy associated with a moving object: kinetic energy (joule, J) = 1/2 × mass (kilogram, kg) × (speed)² ((metre/second)², (m/s)²) KE = 1/2 × m × v²

1.

What is the equation for kinetic energy?

KE = ½ × m × v².

2.

What quantities are needed to calculate the kinetic energy of a moving object?

Its mass and speed.

3.

What is the kinetic energy of a 4 kg object travelling at 5 m/s?

KE = ½ × 4 × 5² = 50 J.

4.

What is the kinetic energy of a 1,000 kg car travelling at 10 m/s?

KE = ½ × 1000 × 10² = 50,000 J.

5.

A 2 kg object has a kinetic energy of 100 J. What is its speed?

v = √(100 ÷ (½ × 2)) = 10 m/s.

6.

What happens to the kinetic energy of an object when its speed is doubled?

It becomes four times greater.

3.3 Draw and interpret diagrams to represent energy transfers

1.

What is an energy transfer diagram used to represent?

How energy moves between different stores or pathways in a system.

2.

What do arrows represent in an energy transfer diagram?

The direction of energy transfer.

3.

What is meant by a useful energy transfer?

A transfer that provides the intended output of the device or system.

4.

What is meant by a wasted or dissipated energy transfer?

An energy transfer that does not contribute usefully to the intended output, transferred to the surroundings.

5.

How could an energy transfer diagram represent the energy transfers in an electric kettle?

Electrical energy → thermal energy in the water, with some energy transferred by heating the kettle and surroundings.

6.

How can an energy transfer diagram show where energy is dissipated?

By showing arrows leaving the useful pathway and transferring energy to the surroundings.

3.4 Explain what is meant by conservation of energy

1.

What does conservation of energy mean?

Energy cannot be created or destroyed; it can only be transferred between stores or transformed.

2.

Can energy be created or destroyed?

No.

3.

What happens to the total amount of energy during an energy transfer?

It remains constant.

4.

What happens to energy when it is described as being wasted?

It has been transferred to less useful energy stores, usually in the surroundings.

5.

Why does calling energy "wasted" not mean that the energy has been destroyed?

Because the energy has been transferred to another store rather than disappearing.

6.

How does conservation of energy apply to a moving object that eventually comes to rest?

Its kinetic energy is transferred to other stores such as thermal energy, so total energy is conserved.

3.5 Analyse the changes involved in the way energy is stored when a system changes, including: a an object projected upwards or up a slope b a moving object hitting an obstacle c an object being accelerated by a constant force d a vehicle slowing down e bringing water to a boil in an electric kettle

1.

What energy store increases when an object is projected upwards?

Its gravitational potential energy store.

2.

What energy transfers occur when a moving object hits an obstacle?

Kinetic energy decreases and is transferred to thermal energy, elastic energy, sound and deformation.

3.

What happens to the energy stores of an object being accelerated by a constant force?

Its kinetic energy store increases as its speed increases.

4.

What happens to the kinetic energy store of a vehicle as it slows down?

It decreases.

5.

What energy transfer occurs when an electric kettle brings water to its boiling point?

Electrical energy is transferred to the thermal energy store of the water.

6.

How is energy conserved when a vehicle slows down and its kinetic energy decreases?

The decreasing kinetic energy is transferred to other stores, mainly thermal energy in the brakes, tyres, road and surroundings.

3.6 Explain that where there are energy transfers in a closed system there is no net change to the total energy in that system

1.

What is meant by a closed system?

A system in which energy does not enter or leave the system.

2.

What happens to the total energy in a closed system during an energy transfer?

It remains constant.

3.

Why is there no net change in the total energy of a closed system?

Because energy is transferred between stores within the system rather than entering or leaving it.

4.

How can energy be transferred within a closed system without changing the total energy?

Energy moves between different stores while the total energy remains unchanged.

5.

What happens to the total energy of a closed system when some energy is dissipated?

It remains constant, although some energy may be transferred to less useful stores.

6.

Why does energy dissipation not violate conservation of energy?

Because the energy is transferred to other stores, rather than being destroyed.

3.7 Explain that mechanical processes become wasteful when they cause a rise in temperature so dissipating energy in heating the surroundings

1.

Why can mechanical processes become wasteful?

When energy is dissipated to the surroundings, usually through friction, rather than being transferred usefully.

2.

How does friction cause energy to be dissipated?

It transfers energy from useful mechanical energy stores to thermal energy stores.

3.

What happens to the temperature of surfaces when friction occurs?

It generally increases.

4.

What energy store increases when friction heats the surroundings?

The thermal energy store.

5.

Why does a rise in temperature indicate that energy has been dissipated?

It shows energy has been transferred to thermal energy stores, making it less useful.

6.

How can friction make a mechanical process less efficient?

Some of the input energy is dissipated as thermal energy instead of being transferred usefully.

3.8 Explain, using examples, how in all system changes energy is dissipated so that it is stored in less useful ways

1.

What is meant by energy being dissipated?

Energy is transferred to less useful energy stores, usually in the surroundings.

2.

In what form is energy commonly dissipated to the surroundings?

Thermal energy, often with some energy transferred by sound.

3.

How is energy dissipated when a moving object slows down due to friction?

Kinetic energy is transferred mainly to thermal energy stores in the object, surface and surroundings.

4.

How can energy be dissipated by an electrical device?

By heating its surroundings and producing unwanted sound.

5.

Why is dissipated energy described as being stored in a less useful way?

Because it is spread into the surroundings and is difficult to transfer back into useful forms.

6.

Give an example of a system change in which energy is dissipated to the surroundings.

A bicycle braking, where kinetic energy is dissipated mainly as thermal energy in the brake pads, wheels and surroundings.

3.9 Explain ways of reducing unwanted energy transfer including through lubrication, thermal insulation

1.

How does lubrication reduce unwanted energy transfer?

By reducing friction between moving surfaces.

2.

Why does lubrication reduce energy dissipation caused by friction?

Less mechanical energy is dissipated as thermal energy.

3.

How does thermal insulation reduce unwanted energy transfer?

By reducing the rate at which thermal energy is transferred between an object and its surroundings.

4.

Why are walls of buildings often fitted with insulating materials?

To reduce thermal energy transfer and slow the loss of thermal energy from the building.

5.

How can double glazing reduce unwanted thermal energy transfer?

By trapping an insulating layer of air or gas between the panes.

6.

Why can reducing unwanted energy transfers increase the efficiency of a system?

More of the supplied energy is transferred usefully.

3.10 Describe the effects of the thickness and thermal conductivity of the walls of a building on its rate of cooling qualitatively

1.

How does increasing the thickness of a building's walls affect its rate of cooling?

It generally reduces the rate of cooling.

2.

How does increasing the thermal conductivity of a wall affect the rate of cooling?

It generally increases the rate of cooling.

3.

Why do materials with low thermal conductivity reduce the rate of cooling?

They transfer thermal energy slowly.

4.

Why does a thicker wall generally reduce the rate of thermal energy transfer?

It provides more material through which thermal energy must be transferred.

5.

Which would cool more slowly: a building with thick, low-conductivity walls or thin, high-conductivity walls?

A building with thick, low-conductivity walls.

6.

How does thermal conductivity affect the suitability of a material for building insulation?

Materials with low thermal conductivity are more suitable for insulation.

3.11 Recall and use the equation: efficiency = useful energy transferred by the device ÷ total energy supplied to the device

1.

What is the equation for efficiency?

Efficiency = useful energy transferred ÷ total energy supplied.

2.

What is meant by useful energy transferred by a device?

The energy transferred in the intended or desired form.

3.

What is meant by total energy supplied to a device?

The total energy transferred to the device as input.

4.

A device receives 500 J of energy and transfers 400 J usefully. What is its efficiency?

Efficiency = 400 ÷ 500 = 0.80.

5.

A device has an efficiency of 0.75 and receives 800 J of energy. How much useful energy does it transfer?

Useful energy = 0.75 × 800 = 600 J.

6.

A device transfers 300 J of useful energy from 600 J supplied. What is its efficiency as a percentage?

Efficiency = 300 ÷ 600 = 0.5 = 50%.

3.12 Explain how efficiency can be increased

1.

What does it mean for a device to have a high efficiency?

It transfers a large proportion of its input energy usefully.

2.

How can reducing unwanted energy transfers increase efficiency?

Less input energy is wasted, so the proportion transferred usefully increases.

3.

How can lubrication increase the efficiency of a mechanical system?

It reduces friction and therefore reduces energy dissipated as thermal energy.

4.

How can thermal insulation increase the efficiency of a system?

It reduces unwanted thermal energy transfer, so more energy remains available for the intended purpose.

5.

Why does reducing energy dissipated to the surroundings increase efficiency?

A greater proportion of the input energy is transferred usefully.

6.

A device becomes more efficient without changing the total energy supplied. What must happen to the useful energy transferred?

It must increase.

3.13 Describe the main energy sources available for use on Earth (including fossil fuels, nuclear fuel, bio-fuel, wind, hydroelectricity, the tides and the Sun), and compare the ways in which both renewable and non-renewable sources are used

1.

What are the main non-renewable energy sources used on Earth?

Fossil fuels (coal, oil and natural gas) and nuclear fuel.

2.

What are the main renewable energy sources used on Earth?

Bio-fuels, wind, hydroelectricity, tidal energy and solar energy.

3.

Why are fossil fuels classified as non-renewable?

They take millions of years to form and are consumed much faster than they are replaced.

4.

Why are wind, hydroelectric, tidal and solar energy classified as renewable?

Their energy sources are naturally replenished.

5.

What is one advantage and one disadvantage of using fossil fuels to generate electricity?

Advantage: reliable, controllable electricity. Disadvantage: burning them releases carbon dioxide and other pollutants.

6.

How does nuclear fuel differ from renewable energy sources in terms of its availability?

Its fuel reserves are finite, whereas renewable sources are naturally replenished on a human timescale.

3.14 Explain patterns and trends in the use of energy resources

1.

What factors can affect the amount of energy obtained from different energy resources?

Availability, cost, demand, reliability, environmental impact, technology and government policy.

2.

Why can the use of renewable energy resources increase over time?

As technology improves, costs fall and the need to reduce environmental impacts increases.

3.

Why might the use of fossil fuels decrease over time?

Concerns about climate change, pollution, finite supplies and the development of renewable alternatives.

4.

How can technological developments affect the use of energy resources?

They can make energy sources more efficient, cheaper, more reliable or easier to use.

5.

How can government policies influence patterns in energy-resource use?

Through taxes, subsidies, regulations, targets and investment in particular energy sources.

6.

Why might different countries have different patterns of energy-resource use?

They have different natural resources, energy demands, economies, technologies and government policies.

4.1 Recall that waves transfer energy and information without transferring matter

1.

What do waves transfer from one place to another?

Energy and information.

2.

Do waves transfer matter from one place to another?

No.

3.

How can a wave transfer energy without transferring matter?

Particles or fields oscillate and pass the disturbance to neighbouring particles or regions, without transporting the particles overall.

4.

How can waves be used to transfer information?

By modulating properties of the wave, such as amplitude or frequency.

5.

What happens to the matter through which a wave travels?

It oscillates about its equilibrium position rather than travelling with the wave overall.

6.

Give one example of a wave transferring energy without transferring matter.

A water wave transferring energy to a floating object without transporting the object with it.

4.2 Describe evidence that with water and sound waves it is the wave and not the water or air itself that travels

1.

What happens to a floating object as a water wave passes it?

It generally moves up and down and may move back and forth, rather than travelling forward with the wave.

2.

What does the motion of a floating object show about whether water is transported by a wave?

It shows that the water oscillates about its equilibrium position while the wave transfers energy forwards.

3.

What evidence shows that air itself does not travel from a sound source to a listener?

Sound can travel through air, but the air particles vibrate about their equilibrium positions rather than travelling to the listener.

4.

What happens to air particles as a sound wave passes through them?

They vibrate back and forth, producing compressions and rarefactions.

5.

Why does the movement of water particles provide evidence that water waves transfer energy rather than water?

Water particles mainly oscillate about their equilibrium positions.

6.

How does the motion of air particles in a sound wave demonstrate that the wave travels rather than the air itself?

Air particles oscillate locally as the disturbance passes from particle to particle.

4.3 Define and use the terms frequency and wavelength as applied to waves

1.

What is meant by the frequency of a wave?

The number of complete waves or oscillations passing a point each second.

2.

What is the SI unit for frequency?

The hertz (Hz).

3.

What is meant by the wavelength of a wave?

The distance between corresponding points on two consecutive waves, such as crest to crest.

4.

What symbol is commonly used for wavelength?

λ (lambda).

5.

What does a higher frequency mean about the number of waves passing a point each second?

More waves pass a point each second.

6.

How is wavelength measured on a transverse wave?

As the horizontal distance between corresponding points on consecutive waves, such as crest to crest.

4.4 Use the terms amplitude, period, wave velocity and wavefront as applied to waves

1.

What is meant by the amplitude of a wave?

The maximum displacement of a point on a wave from its equilibrium position.

2.

What is meant by the period of a wave?

The time taken for one complete wave or oscillation to pass a point.

3.

What is meant by wave velocity?

The speed and direction in which a wave travels.

4.

What is a wavefront?

A line or surface joining points on a wave that are in the same phase.

5.

What is the relationship between the period and frequency of a wave?

f = 1 ÷ T and T = 1 ÷ f.

6.

How does the amplitude of a wave relate to the maximum displacement from its equilibrium position?

Amplitude is the maximum displacement from the equilibrium position.

4.5 Describe the difference between longitudinal and transverse waves by referring to sound, electromagnetic, seismic and water waves

1.

What is the difference between a longitudinal wave and a transverse wave?

In a longitudinal wave oscillations are parallel to the direction of travel; in a transverse wave they are perpendicular.

2.

In which direction do particles vibrate compared with the direction of travel in a longitudinal wave?

Parallel.

3.

In which direction do particles vibrate compared with the direction of travel in a transverse wave?

Perpendicular.

4.

What type of wave is sound in air?

A longitudinal wave.

5.

What type of wave are electromagnetic waves?

Transverse waves.

6.

How can seismic and water waves demonstrate transverse and longitudinal wave behaviour?

Seismic waves can be longitudinal or transverse, while water surface waves involve a combination of both types of motion.

4.6 Recall and use both the equations below for all waves: wave speed (metre/second, m/s) = frequency (hertz, Hz) × wavelength (metre, m) v = f × λ; wave speed (metre/second, m/s) = distance (metre, m) ÷ time (second, s) v = x ÷ t

1.

What is the equation linking wave speed, frequency and wavelength?

v = f × λ.

2.

What is the equation linking wave speed, distance and time?

v = x ÷ t.

3.

A wave has a frequency of 5 Hz and a wavelength of 2 m. What is its speed?

v = 5 × 2 = 10 m/s.

4.

A wave travels at 300 m/s and has a frequency of 150 Hz. What is its wavelength?

λ = 300 ÷ 150 = 2 m.

5.

A wave travels 120 m in 4 s. What is its speed?

v = 120 ÷ 4 = 30 m/s.

6.

A wave has a speed of 20 m/s and a wavelength of 4 m. What is its frequency?

f = 20 ÷ 4 = 5 Hz.

4.7 Describe how to measure the velocity of sound in air and ripples on water surfaces

1.

How can the velocity of sound in air be measured experimentally?

Place two microphones a known distance apart, measure the time delay between the sound reaching them, and calculate the speed.

2.

What measurements are needed to calculate the velocity of sound?

The distance between the microphones and the time taken for the sound to travel between them.

3.

How can the velocity of ripples on a water surface be measured?

By measuring the distance travelled by a ripple over a known time, or by measuring frequency and wavelength.

4.

How can a known distance and measured time be used to calculate wave velocity?

v = x ÷ t.

5.

Why can a large distance between two microphones improve the measurement of the speed of sound?

A larger distance gives a larger time delay, making the timing difference easier to measure accurately.

6.

What equipment could be used to measure the wavelength of ripples on a water surface?

A ruler or metre rule and a stroboscope or camera.

4.8P Calculate depth or distance from time and wave velocity

1.

What equation can be used to calculate distance from wave velocity and time?

x = v × t.

2.

A wave travels at 1,500 m/s for 2 s. What distance does it travel?

x = 1500 × 2 = 3000 m.

3.

A sound wave travels at 340 m/s for 0.5 s. What distance does it travel?

x = 340 × 0.5 = 170 m.

4.

A wave travels 600 m at 300 m/s. How long does the journey take?

t = 600 ÷ 300 = 2 s.

5.

An echo returns 0.4 s after a sound pulse is emitted. If the sound speed is 340 m/s, what total distance does the sound travel?

x = 340 × 0.4 = 136 m.

6.

An echo takes 0.6 s to return from the seabed. If sound travels through water at 1,500 m/s, what is the depth of the water?

Total distance = 1500 × 0.6 = 900 m; depth = 900 ÷ 2 = 450 m.

4.9P Describe the effects of a reflection b refraction c transmission d absorption of waves at material interfaces

1.

What happens to a wave during reflection?

It changes direction and remains in the original medium.

2.

What happens to a wave during refraction?

It changes speed and usually changes direction as it enters a different medium.

3.

What happens to a wave during transmission?

It passes through a material or boundary into another region.

4.

What happens to a wave during absorption?

Its energy is transferred to the material, often increasing its thermal energy.

5.

What happens to the direction of a wave when it is reflected?

It changes direction according to the law of reflection.

6.

What happens to the energy of a wave when it is absorbed by a material?

It is transferred to the material and is no longer carried by the wave.

4.10 Explain how waves will be refracted at a boundary in terms of the change of direction and speed

1.

What happens to the speed of a wave when it enters a different medium?

It may change.

2.

Why does a wave change direction when it is refracted?

Because the wave changes speed at the boundary, causing its direction to change unless it enters along the normal.

3.

What happens to the direction of a wave entering a medium where its speed decreases?

It generally bends towards the normal.

4.

What happens to the direction of a wave entering a medium where its speed increases?

It generally bends away from the normal.

5.

What happens to the frequency of a wave when it crosses a boundary between two media?

It does not change.

6.

How are changes in wave speed and direction related during refraction?

Since v = f × λ and frequency stays constant, a change in speed causes a change in wavelength and direction.

4.11 Recall that different substances may absorb, transmit, refract or reflect waves in ways that vary with wavelength

1.

What does it mean for a material to absorb a wave?

The material takes in energy carried by the wave.

2.

What does it mean for a material to transmit a wave?

The wave passes through the material.

3.

What does it mean for a material to reflect a wave?

The wave bounces back from a boundary.

4.

What does it mean for a material to refract a wave?

The wave changes speed and usually direction as it enters the material.

5.

Why can the same material interact differently with waves of different wavelengths?

The material's properties and structure affect how strongly it interacts with each wavelength.

6.

How can wavelength affect whether a wave is absorbed or transmitted by a substance?

A material may absorb some wavelengths while allowing others to be transmitted.

4.12P Describe the processes which convert wave disturbances between sound waves and vibrations in solids, and a explain why such processes only work over a limited frequency range b use this to explain the way the human ear works

1.

How can a sound wave cause vibrations in a solid?

The sound's pressure variations exert forces on the solid.

2.

How can vibrations in a solid produce sound waves?

The vibrating solid causes pressure variations in the surrounding medium.

3.

Why do processes converting sound waves into vibrations only work over a limited frequency range?

The response of the material or system depends on frequency.

4.

What part of the human ear vibrates in response to sound waves?

The eardrum.

5.

How are vibrations in the eardrum transferred through the middle ear?

By the three small bones — the ossicles — to the cochlea.

6.

How does the human ear convert sound vibrations into signals that can be processed by the brain?

The cochlea converts mechanical vibrations into electrical nerve signals.

4.13P Recall that sound with frequencies greater than 20 000 hertz, Hz, is known as ultrasound

1.

What is ultrasound?

Sound with a frequency greater than 20,000 Hz.

2.

What frequency range defines ultrasound?

Above 20,000 Hz.

3.

Is a sound wave with a frequency of 25,000 Hz ultrasound?

Yes, because it is greater than 20,000 Hz.

4.

Is a sound wave with a frequency of 15,000 Hz ultrasound?

No, because it is below 20,000 Hz.

5.

What is the minimum frequency required for a sound wave to be classified as ultrasound?

Greater than 20,000 Hz.

6.

Why can humans not normally hear ultrasound?

The human hearing range does not extend above about 20,000 Hz.

4.14P Recall that sound with frequencies less than 20 hertz, Hz, is known as infrasound

1.

What is infrasound?

Sound with a frequency less than 20 Hz.

2.

What frequency range defines infrasound?

Below 20 Hz.

3.

Is a sound wave with a frequency of 10 Hz infrasound?

Yes, because it is below 20 Hz.

4.

Is a sound wave with a frequency of 25 Hz infrasound?

No, because it is above 20 Hz.

5.

What is the maximum frequency for a sound wave to be classified as infrasound?

Less than 20 Hz.

6.

Why can humans not normally hear infrasound?

The human hearing range does not extend below about 20 Hz.

4.15P Explain uses of ultrasound and infrasound, including a sonar b foetal scanning c exploration of the Earth's core

1.

How is ultrasound used in sonar?

Pulses are sent into water and reflected from objects or the seabed; the echo time is used to determine distance or depth.

2.

How can ultrasound be used to produce images during foetal scanning?

It is transmitted into the body and reflected at boundaries between different tissues.

3.

Why is ultrasound suitable for foetal scanning?

It is non-ionising and can produce images from echoes at tissue boundaries.

4.

How can infrasound provide information about the Earth's interior?

Through low-frequency seismic waves and their behaviour as they travel through the Earth.

5.

Why can seismic waves be useful for exploring the Earth's core?

Their speeds, paths, reflections and refractions change when they encounter different materials.

6.

How can the reflection or refraction of waves provide information about structures inside the Earth?

Changes in the wave's path or return time indicate changes in the materials through which the wave travels.

4.16P Describe how changes, if any, in velocity, frequency and wavelength, in the transmission of sound waves from one medium to another are inter-related

1.

What happens to the speed of a sound wave when it enters a different medium?

It usually changes.

2.

What happens to the frequency of a sound wave when it enters a different medium?

It does not change.

3.

What happens to the wavelength of a sound wave when its speed changes but its frequency remains constant?

It changes in the same proportion as the speed.

4.

Which equation links wave speed, frequency and wavelength?

v = f × λ.

5.

A sound wave enters a medium where its speed increases while its frequency remains constant. What happens to its wavelength?

It increases.

6.

A sound wave has a frequency of 500 Hz and a speed of 340 m/s. What is its wavelength?

λ = 340 ÷ 500 = 0.68 m.

4.17 Core Practical: Investigate the suitability of equipment to measure the speed, frequency and wavelength of a wave in a solid and a fluid

1.

What measurements are needed to calculate the speed of a wave?

Frequency and wavelength (v = f × λ), or distance and time (v = x ÷ t).

2.

How can the frequency of a wave be measured experimentally?

By counting the number of complete waves passing a point in a known time, or using a frequency-measuring device.

3.

How can the wavelength of a wave be measured?

By measuring the distance between corresponding points on consecutive waves.

4.

How can the equation v = f × λ be used to determine wave speed?

Measure the frequency and wavelength, then multiply them.

5.

What equipment could be used to investigate waves travelling through a solid?

A signal generator, vibration source, solid rod or string, microphone/sensor and oscilloscope.

6.

What equipment could be used to investigate waves travelling through a fluid?

A ripple tank, lamp, ruler, signal generator and vibration source, with a camera or stroboscope.

5.1P Explain, with the aid of ray diagrams, reflection, refraction and total internal reflection (TIR), including the law of reflection and critical angle

1.

What is reflection of light?

The change in direction of light when it bounces off a surface and remains in the original medium.

2.

What is refraction of light?

The change in direction of light caused by a change in its speed when it passes from one medium to another.

3.

What is the law of reflection?

The angle of incidence equals the angle of reflection, measured from the normal.

4.

What is meant by the critical angle?

The angle of incidence in the higher refractive index medium for which the angle of refraction is 90°.

5.

What two conditions are required for total internal reflection to occur?

Light must travel from a higher to a lower refractive index medium, and the angle of incidence must exceed the critical angle.

6.

What happens to a ray of light when it travels from a higher refractive index medium to a lower refractive index medium at an angle greater than the critical angle?

It undergoes total internal reflection and is reflected completely back into the higher refractive index medium.

5.2P Explain the difference between specular and diffuse reflection

1.

What is specular reflection?

Reflection from a smooth surface in which parallel incident rays remain parallel after reflection.

2.

What is diffuse reflection?

Reflection from a rough surface in which parallel incident rays are reflected in different directions.

3.

How do the surfaces involved in specular and diffuse reflection differ?

Specular reflection occurs at smooth surfaces, diffuse reflection at rough or uneven surfaces.

4.

Why does a smooth surface produce specular reflection?

Its normal is effectively the same across the reflecting area, so reflected rays remain parallel.

5.

Why does a rough surface produce diffuse reflection?

Its normals are at different angles, so reflected rays travel in different directions.

6.

How do the reflected rays differ between specular and diffuse reflection?

In specular reflection they are parallel or regularly arranged; in diffuse reflection they are scattered.

5.3P Explain how colour of light is related to a differential absorption at surfaces b transmission of light through filters

1.

Why does an object appear to have a particular colour under white light?

It reflects or transmits some wavelengths of visible light more than others.

2.

How can differential absorption at a surface affect the colour of an object?

A surface absorbs some wavelengths more strongly than others, and the remaining reflected light determines the colour seen.

3.

What happens to different wavelengths of light when white light passes through a coloured filter?

Some wavelengths are transmitted and others are absorbed.

4.

Why does a red filter transmit mainly red light?

It transmits mainly red wavelengths and absorbs most other visible wavelengths.

5.

What happens to wavelengths that are absorbed by a coloured filter?

They are not transmitted; their energy is absorbed by the material.

6.

Why does the colour seen through a filter depend on the wavelengths it transmits?

These are the wavelengths that reach the observer.

5.4P Relate the power of a lens to its focal length and shape

1.

What is meant by the power of a lens?

A measure of how strongly the lens converges or diverges light.

2.

What is the relationship between the power and focal length of a lens?

Power is inversely proportional to focal length.

3.

What is the equation for the power of a lens?

P = 1 ÷ f, where P is in dioptres and f in metres.

4.

What is the power of a lens with a focal length of 0.5 m?

P = 1 ÷ 0.5 = 2 D.

5.

What is the focal length of a lens with a power of 4 dioptres?

f = 1 ÷ 4 = 0.25 m.

6.

How does the shape of a lens affect its power?

A lens with greater curvature generally has greater power and a shorter focal length.

5.5P Use ray diagrams to show the similarities and differences in the refraction of light by converging and diverging lenses

1.

What does a converging lens do to parallel rays of light?

Refracts them so that they meet at the principal focus.

2.

What does a diverging lens do to parallel rays of light?

Refracts them so that they spread out.

3.

Where do parallel rays converge after passing through a converging lens?

At the principal focus on the opposite side of the lens.

4.

How do rays appear to behave after passing through a diverging lens?

They spread out as though they came from a principal focus on the same side as the object.

5.

What is the main difference between the ray diagrams for converging and diverging lenses?

A converging-lens diagram shows rays meeting; a diverging-lens diagram shows rays spreading apart.

6.

What happens to a ray travelling through the optical centre of a thin lens?

It passes through without significant deviation.

5.6P Explain the effects of different types of lens in producing real and virtual images

1.

What is a real image?

An image formed when light rays actually converge at a point, which can be formed on a screen.

2.

What is a virtual image?

An image formed when light rays only appear to come from a point, which cannot be formed on a screen.

3.

Which type of lens can produce both real and virtual images depending on the object's position?

A converging lens.

4.

What type of image is normally produced by a diverging lens?

A virtual, upright and diminished image.

5.

Can a real image be formed on a screen?

Yes.

6.

How does the position of an object affect the type of image formed by a converging lens?

An object outside the focal length produces a real image; inside the focal length produces a virtual image.

5.7 Recall that all electromagnetic waves are transverse, that they travel at the same speed in a vacuum

1.

What type of wave are all electromagnetic waves?

Transverse waves.

2.

What is the speed of electromagnetic waves in a vacuum?

Approximately 3.0 × 10⁸ m/s.

3.

Do all electromagnetic waves travel at the same speed in a vacuum?

Yes.

4.

How are vibrations oriented compared with the direction of travel in a transverse wave?

Perpendicular.

5.

Do electromagnetic waves require a medium to travel through a vacuum?

No.

6.

Why can electromagnetic waves travel through empty space?

They consist of oscillating electric and magnetic fields that sustain each other.

5.8 Explain, with examples, that all electromagnetic waves transfer energy from source to observer

1.

What do electromagnetic waves transfer from a source to an observer?

Energy.

2.

How does visible light transfer energy from the Sun to Earth?

Radiant energy is transferred and can be absorbed and converted into other forms.

3.

How do infrared waves transfer energy from a warm object?

They transfer energy to objects and surfaces that absorb the radiation.

4.

How do microwaves transfer energy to food?

They cause molecules in the food to absorb electromagnetic radiation, increasing thermal energy.

5.

How can gamma rays transfer energy to cells in the body?

They are absorbed by matter in the body.

6.

Why can electromagnetic waves transfer energy through a vacuum?

They do not require particles of a medium to carry the disturbance.

5.9 Core Practical: Investigate refraction in rectangular glass blocks in terms of the interaction of electromagnetic waves with matter

1.

What happens to a ray of light when it enters a rectangular glass block at an angle?

It changes speed and refracts towards the normal.

2.

What happens to the ray when it leaves the glass block?

It changes speed again and refracts away from the normal.

3.

What equipment can be used to investigate refraction through a rectangular glass block?

A rectangular glass block, ray box or laser, paper, ruler, protractor and pencil.

4.

How can the angle of incidence and angle of refraction be measured?

Draw the normal at the boundary and use a protractor to measure the angles.

5.

Why does light change direction when it enters glass from air?

Its speed changes when it enters glass from air.

6.

How can a ray diagram be used to investigate refraction through a glass block?

Trace the incident, refracted and emergent rays, draw the normals and measure the angles with a protractor.

5.10 Recall the main groupings of the continuous electromagnetic spectrum including (in order) radio waves, microwaves, infrared, visible (including the colours of the visible spectrum), ultraviolet, x-rays and gamma rays

1.

What is the correct order of the electromagnetic spectrum from lowest to highest frequency?

Radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, gamma rays.

2.

Which electromagnetic wave has the longest wavelength?

Radio waves.

3.

Which electromagnetic wave has the highest frequency?

Gamma rays.

4.

What are the colours of visible light in order from longest to shortest wavelength?

Red, orange, yellow, green, blue, indigo, violet.

5.

Which region of the electromagnetic spectrum lies between microwaves and visible light?

Infrared.

6.

Which region of the electromagnetic spectrum lies between ultraviolet and gamma rays?

X-rays.

5.11 Describe the electromagnetic spectrum as continuous from radio waves to gamma rays and that the radiations within it can be grouped in order of decreasing wavelength and increasing frequency

1.

What does it mean that the electromagnetic spectrum is continuous?

It covers a continuous range of frequencies and wavelengths, rather than isolated values.

2.

In what order does wavelength decrease across the electromagnetic spectrum?

Radio waves → microwaves → infrared → visible → ultraviolet → x-rays → gamma rays.

3.

In what order does frequency increase across the electromagnetic spectrum?

Radio waves → microwaves → infrared → visible → ultraviolet → x-rays → gamma rays.

4.

Which has the greater frequency: infrared or ultraviolet?

Ultraviolet.

5.

Which has the longer wavelength: microwaves or visible light?

Microwaves.

6.

What happens to frequency as wavelength decreases across the electromagnetic spectrum?

Frequency increases.

5.12 Recall that our eyes can only detect a limited range of frequencies of electromagnetic radiation

1.

Which region of the electromagnetic spectrum can human eyes detect?

Visible light.

2.

Why can humans not normally see infrared radiation?

Its frequency is below the range detectable by the human eye.

3.

Why can humans not normally see ultraviolet radiation?

Its frequency is above the range detectable by the human eye.

4.

What is meant by the visible region of the electromagnetic spectrum?

The limited range of frequencies detectable by the human eye.

5.

How does the visible range compare with the full electromagnetic spectrum?

It is only a very small part.

6.

Why is visible light only a small part of the electromagnetic spectrum?

The spectrum contains a much wider range of frequencies than those detectable by human eyes.

5.13 Recall that different substances may absorb, transmit, refract or reflect electromagnetic waves in ways that vary with wavelength

1.

What does it mean for a substance to absorb electromagnetic radiation?

It takes in energy from the radiation.

2.

What does it mean for a substance to transmit electromagnetic radiation?

The radiation passes through the substance.

3.

What does it mean for a substance to reflect electromagnetic radiation?

The radiation bounces back from a surface or boundary.

4.

What does it mean for a substance to refract electromagnetic radiation?

It changes speed and usually direction as it enters the substance.

5.

Why can a substance interact differently with electromagnetic waves of different wavelengths?

Its electrical and structural properties affect how it interacts with the radiation.

6.

Why might a material transmit visible light but absorb infrared radiation?

Its absorption and transmission properties depend on wavelength.

5.14 Explain the effects of differences in the velocities of electromagnetic waves in different substances

1.

What happens to the speed of an electromagnetic wave when it enters a different substance?

It usually changes.

2.

Why can an electromagnetic wave be refracted when it enters a different substance?

Its speed changes at the boundary between substances.

3.

What happens to the direction of an electromagnetic wave when its speed changes at a boundary?

It may change, producing refraction.

4.

Does the frequency of an electromagnetic wave change when it enters a different medium?

No.

5.

What happens to wavelength when the speed of an electromagnetic wave decreases but frequency remains constant?

It decreases.

6.

Why does a difference in wave speed between two substances cause refraction?

Different substances allow electromagnetic waves to travel at different speeds, changing direction at a boundary.

5.15P Explain that all bodies emit radiation, that the intensity and wavelength distribution of any emission depends on their temperature

1.

What type of radiation is emitted by all bodies?

Electromagnetic radiation, including infrared radiation.

2.

What happens to the intensity of emitted radiation as an object's temperature increases?

It increases.

3.

How does temperature affect the wavelengths of radiation emitted by an object?

As temperature increases, the distribution shifts towards shorter wavelengths.

4.

Which emits more thermal radiation: a hot object or a cooler object?

A hot object.

5.

How does the wavelength distribution of radiation change as an object's temperature increases?

A greater proportion of the radiation is at shorter wavelengths.

6.

Why can thermal imaging detect differences in the temperatures of objects?

Objects at different temperatures emit different amounts of infrared radiation.

5.16P Explain that for a body to be at a constant temperature it needs to radiate the same average power that it absorbs

1.

What condition must be met for an object to remain at a constant temperature?

Its average power emitted must equal its average power absorbed.

2.

What happens when the average power radiated by an object equals the average power absorbed?

Its temperature remains constant.

3.

What happens to an object's temperature if it absorbs more power than it radiates?

It increases.

4.

What happens to an object's temperature if it radiates more power than it absorbs?

It decreases.

5.

Why does a constant-temperature object have no net change in its energy?

Energy absorbed equals energy emitted.

6.

How is the balance between absorbed and emitted radiation related to temperature?

An object changes temperature until the average powers absorbed and emitted become equal.

5.17P Explain what happens to a body if the average power it radiates is less or more than the average power that it absorbs

1.

What happens to the temperature of a body if it absorbs more power than it radiates?

It increases.

2.

What happens to the temperature of a body if it radiates more power than it absorbs?

It decreases.

3.

What happens when absorbed and radiated powers are equal?

The temperature remains constant.

4.

Why does a body warm up when its absorbed power is greater than its emitted power?

More energy enters it than leaves it, increasing its thermal energy.

5.

Why does a body cool down when its emitted power is greater than its absorbed power?

More energy leaves it than enters it, decreasing its thermal energy.

6.

What happens to the temperature of a body when the difference between absorbed and emitted power is zero?

It remains constant.

5.18P Explain how the temperature of the Earth is affected by factors controlling the balance between incoming radiation and radiation emitted

1.

What are the main sources of incoming radiation reaching Earth?

Solar electromagnetic radiation from the Sun.

2.

What happens to Earth's temperature when incoming radiation increases while emitted radiation remains constant?

It increases.

3.

What happens to Earth's temperature when emitted radiation increases while incoming radiation remains constant?

It decreases.

4.

How can changes in Earth's atmosphere affect the balance between incoming and outgoing radiation?

By affecting the absorption, transmission and emission of infrared radiation.

5.

Why does Earth reach a stable average temperature when incoming and emitted radiation are balanced?

The average incoming power equals the average outgoing power.

6.

How can an increase in absorbed radiation affect Earth's average temperature?

It causes the temperature to increase until outgoing radiation increases enough to restore balance.

5.19P Core Practical: Investigate how the nature of a surface affects the amount of thermal energy radiated or absorbed

1.

How does the nature of a surface affect thermal radiation?

It affects how effectively the surface emits and absorbs infrared radiation.

2.

Which type of surface is generally a better emitter of infrared radiation: dull or shiny?

A dull, dark surface.

3.

Which type of surface is generally a better absorber of infrared radiation: dull or shiny?

A dull, dark surface.

4.

What equipment could be used to compare the thermal radiation emitted by different surfaces?

Identical containers with different surface finishes, a heat source, thermometers and a stopwatch.

5.

What variables should be controlled when comparing the thermal radiation from different surfaces?

Initial temperature, mass of material, container size, heating time, heat source and surrounding conditions.

6.

How could the results of this practical be used to compare the emissivity of different surfaces?

Compare the rate of temperature change or radiation measurements for each surface.

5.20 Recall that the potential danger associated with an electromagnetic wave increases with increasing frequency

1.

How does the potential danger of electromagnetic radiation change as frequency increases?

It generally increases.

2.

Which is potentially more dangerous: infrared or ultraviolet radiation?

Ultraviolet.

3.

Which is potentially more dangerous: visible light or x-rays?

X-rays.

4.

Which electromagnetic waves have the highest frequencies?

Gamma rays.

5.

Why can high-frequency electromagnetic radiation be more damaging to living cells?

It has higher energy per photon.

6.

Which is potentially more dangerous: microwaves or gamma rays?

Gamma rays.

5.21 Describe the harmful effects on people of excessive exposure to electromagnetic radiation, including: a microwaves: internal heating of body cells b infrared: skin burns c ultraviolet: damage to surface cells and eyes, leading to skin cancer and eye conditions d x-rays and gamma rays: mutation or damage to cells in the body

1.

What harmful effect can excessive exposure to microwaves have on body cells?

Internal heating of body tissues and cells.

2.

What harmful effect can excessive exposure to infrared radiation have on the skin?

Skin burns.

3.

How can excessive ultraviolet exposure damage skin and eyes?

It can cause skin damage and eye disorders.

4.

How can excessive ultraviolet exposure increase the risk of skin cancer?

It can damage DNA in skin cells.

5.

How can x-rays damage cells in the body?

They can damage or mutate cells, potentially causing cancer if exposure is excessive.

6.

How can excessive exposure to gamma rays affect cells in the body?

They can cause cell damage and mutations, potentially causing cancer.

5.22 Describe some uses of electromagnetic radiation a radio waves: including broadcasting, communications and satellite transmissions b microwaves: including cooking, communications and satellite transmissions c infrared: including cooking, thermal imaging, short range communications, optical fibres, television remote controls and security systems d visible light: including vision, photography and illumination e ultraviolet: including security marking, fluorescent lamps, detecting forged bank notes and disinfecting water f x-rays: including observing the internal structure of objects, airport security scanners and medical x-rays g gamma rays: including sterilising food and medical equipment, and the detection of cancer and its treatment

1.

What are radio waves used for in broadcasting and communications?

Broadcasting, communications and satellite transmissions.

2.

What are microwaves used for in cooking and satellite communications?

Cooking, communications and satellite transmissions.

3.

What are infrared waves used for in thermal imaging and television remote controls?

Cooking, thermal imaging, short-range communications, optical fibres, TV remote controls and security systems.

4.

What are some uses of visible light?

Vision, photography and illumination.

5.

What are ultraviolet waves used for in security marking and disinfecting water?

Security marking, fluorescent lamps, detecting forged bank notes and disinfecting water.

6.

What are x-rays and gamma rays used for in medicine and security?

X-rays for medical imaging and airport security scanners; gamma rays for sterilising food and equipment and detecting/treating cancer.

5.23 Recall that radio waves can be produced by, or can themselves induce, oscillations in electrical circuits

1.

How can radio waves be produced?

By oscillating electric charges or alternating currents in an aerial.

2.

What happens in an electrical circuit when radio waves induce oscillations?

They cause alternating currents or voltages to oscillate at the wave's frequency.

3.

What type of motion in an electrical circuit can produce radio waves?

Oscillating electric current or charge in an aerial.

4.

How can an oscillating electrical current produce electromagnetic radiation?

Accelerating charges generate changing electric and magnetic fields that propagate outward.

5.

How can radio waves cause oscillations in an electrical circuit?

They induce alternating currents or voltages in a receiving aerial or circuit.

6.

Why are oscillating electrical charges important in the production and detection of radio waves?

Their changing fields produce electromagnetic waves, while incoming waves can induce oscillations for detection.

5.24 Recall that changes in atoms and nuclei can a generate radiations over a wide frequency range b be caused by absorption of a range of radiations

1.

How can changes in atoms generate electromagnetic radiation?

Electrons moving between different energy levels release energy as photons.

2.

How can changes in atomic nuclei generate electromagnetic radiation?

Particularly gamma radiation from changes in the nucleus.

3.

What determines the frequency of radiation produced by changes in atoms or nuclei?

The energy difference associated with the atomic or nuclear change.

4.

How can atoms absorb electromagnetic radiation?

When the energy of the radiation matches an allowed energy change within the atom.

5.

How can nuclei be affected by the absorption of electromagnetic radiation?

The radiation may have suitable energy to produce a nuclear transition or other change.

6.

Why can changes in atoms and nuclei produce or absorb radiation across a wide range of frequencies?

They have different possible energy changes.

6.1 Describe an atom as a positively charged nucleus, consisting of protons and neutrons, surrounded by negatively charged electrons, with the nuclear radius much smaller than that of the atom and with almost all of the mass in the nucleus

1.

What particles make up the nucleus of an atom?

Protons and neutrons.

2.

What is the charge of the nucleus?

Positive.

3.

What particles surround the nucleus?

Negatively charged electrons.

4.

How does the radius of the nucleus compare with the radius of the atom?

It is much smaller.

5.

Where is almost all of the mass of an atom concentrated?

In the nucleus.

6.

Why is an atom overall electrically neutral when it contains equal numbers of protons and electrons?

The positive and negative charges cancel out.

6.2 Recall the typical size (order of magnitude) of atoms and small molecules

1.

What is the typical order of magnitude of the radius of an atom?

10⁻¹⁰ m.

2.

What is the approximate size of an atom in metres?

About 1 × 10⁻¹⁰ m.

3.

What is meant by the order of magnitude of a measurement?

The power of ten that gives its approximate size.

4.

How does the size of an atom compare with everyday objects?

Atoms are enormously smaller; a tiny grain of dust contains many billions of atoms.

5.

What is the approximate order of magnitude of the size of a small molecule?

Also approximately 10⁻¹⁰ m.

6.

Why are atoms and small molecules described as being extremely small?

Their dimensions are around one ten-billionth of a metre.

6.3 Describe the structure of nuclei of isotopes using the terms atomic (proton) number and mass (nucleon) number and using symbols in the format ¹³₆C

1.

What does the atomic number of an element represent?

The number of protons in the nucleus.

2.

What does the mass number of an isotope represent?

The total number of protons and neutrons in the nucleus.

3.

How can the number of neutrons in a nucleus be calculated from its mass number and atomic number?

Number of neutrons = mass number − atomic number.

4.

How many protons and neutrons are in a carbon-13 nucleus, ¹³₆C?

6 protons and 7 neutrons.

5.

What information does the symbol ²³₁₁Na provide about a sodium nucleus?

11 protons and 12 neutrons.

6.

How are isotopes represented using atomic number and mass number?

As ᴬZX, where A is the mass number, Z the atomic number and X the element symbol.

6.4 Recall that the nucleus of each element has a characteristic positive charge, but that isotopes of an element differ in mass by having different numbers of neutrons

1.

What determines the positive charge of an atomic nucleus?

Its number of protons.

2.

Why do all atoms of the same element have the same number of protons?

The proton number defines the element.

3.

What is an isotope?

An atom of the same element with the same number of protons but a different number of neutrons.

4.

How do isotopes of the same element differ?

In their number of neutrons and therefore their mass numbers.

5.

Why do isotopes of the same element have different masses?

They contain different numbers of neutrons.

6.

How many neutrons are in carbon-12 and carbon-14?

Carbon-12 has 6 neutrons; carbon-14 has 8 neutrons.

6.5 Recall the relative masses and relative electric charges of protons, neutrons, electrons and positrons

1.

What is the relative mass and relative charge of a proton?

Relative mass 1, relative charge +1.

2.

What is the relative mass and relative charge of a neutron?

Relative mass 1, relative charge 0.

3.

What is the relative mass and relative charge of an electron?

Relative mass approximately 1/1840, relative charge −1.

4.

What is the relative mass and relative charge of a positron?

Relative mass approximately 1/1840, relative charge +1.

5.

Which has approximately the same mass as an electron but opposite charge?

A positron.

6.

Which of the proton, neutron, electron and positron has zero electric charge?

The neutron.

6.6 Recall that in an atom the number of protons equals the number of electrons and is therefore neutral

1.

Why is an atom electrically neutral?

Its positive proton charge balances its negative electron charge.

2.

What is the relationship between the number of protons and electrons in a neutral atom?

They are equal.

3.

How many electrons are present in a neutral atom with 8 protons?

8 electrons.

4.

How many protons are present in a neutral atom with 17 electrons?

17 protons.

5.

What happens to the electrical neutrality of an atom if it loses an electron?

It becomes a positive ion.

6.

What happens to the electrical neutrality of an atom if it gains an electron?

It becomes a negative ion.

6.7 Recall that in each atom its electrons orbit the nucleus at different set distances from the nucleus

1.

What do electrons do around the nucleus?

They occupy specific electron shells or energy levels.

2.

What determines the set distances at which electrons orbit the nucleus?

The electron's allowed energy levels.

3.

Are all electrons in an atom at the same distance from the nucleus?

No; they can occupy different shells.

4.

What is meant by an electron shell?

A set energy level or region around the nucleus occupied by electrons.

5.

Where are the electrons with the lowest energy generally found?

In the shell closest to the nucleus.

6.

How does the distance of an electron from the nucleus relate to its energy level?

Electrons farther from the nucleus generally occupy higher energy levels.

6.8 Explain that electrons change orbit when there is absorption or emission of electromagnetic radiation

1.

What happens to an electron when an atom absorbs electromagnetic radiation?

It moves to a higher energy level.

2.

What happens to an electron when an atom emits electromagnetic radiation?

It moves to a lower energy level.

3.

Why does an electron move to a higher energy level when it absorbs energy?

It gains the energy from the absorbed radiation.

4.

Why does an electron emit electromagnetic radiation when moving to a lower energy level?

It releases its excess energy as radiation.

5.

What determines the frequency of electromagnetic radiation emitted by an electron?

The energy difference between the two electron energy levels (E = hf).

6.

How is electromagnetic radiation involved in changes between electron energy levels?

It is absorbed or emitted when electrons change between allowed energy levels.

6.9 Explain how atoms may form positive ions by losing outer electrons

1.

What is a positive ion?

An atom or group of atoms with an overall positive charge.

2.

How can an atom become a positive ion?

By losing one or more electrons.

3.

Why does losing an electron give an atom a positive charge?

It removes negative charge while the number of protons stays the same.

4.

Which electrons are most likely to be lost when an atom forms a positive ion?

The outermost electrons.

5.

What happens to the number of protons when an atom loses an electron?

It does not change.

6.

What charge does an atom have after losing two electrons?

+2.

6.10 Recall that alpha, β− (beta minus), β+ (positron), gamma rays and neutron radiation are emitted from unstable nuclei in a random process

1.

What type of nucleus emits radioactive radiation?

An unstable nucleus.

2.

Which five types of radiation can be emitted from unstable nuclei?

Alpha, β−, β+, gamma and neutron radiation.

3.

What is emitted during beta minus decay?

A high-speed electron.

4.

What is emitted during beta plus decay?

A positron.

5.

Is it possible to predict exactly when a particular unstable nucleus will decay?

No.

6.

Why is radioactive decay described as a random process?

The time at which an individual unstable nucleus decays cannot be predicted.

6.11 Recall that alpha, β− (beta minus), β+ (positron) and gamma rays are ionising radiations

1.

What is ionising radiation?

Radiation with enough energy to remove electrons from atoms or molecules, forming ions.

2.

Which four types of radiation in the specification are ionising?

Alpha, β−, β+ and gamma.

3.

Is alpha radiation ionising?

Yes, strongly ionising.

4.

Is gamma radiation ionising?

Yes, although less strongly than alpha.

5.

What happens to an atom when ionising radiation passes through it?

Electrons can be removed, producing positive ions and free electrons.

6.

Why can ionising radiation damage living tissue?

It can break chemical bonds and damage DNA.

6.12 Explain what is meant by background radiation

1.

What is background radiation?

Low-level ionising radiation that is continually present in the environment.

2.

Where is background radiation found?

Everywhere, including indoors and outdoors.

3.

Is background radiation present even when no radioactive source has deliberately been introduced?

Yes.

4.

Why must background radiation be considered when measuring radioactivity?

A detector records background radiation as well as radiation from the source being investigated.

5.

Why is background radiation described as being present all around us?

It comes from natural sources on Earth and from space.

6.

How can background radiation affect measurements made using a Geiger–Müller tube?

It can make the measured activity higher than the activity due only to the source.

6.13 Describe the origins of background radiation from Earth and space

1.

What are the two broad origins of background radiation?

Natural sources on Earth and cosmic radiation from space.

2.

How do rocks and soil contribute to background radiation?

They can contain naturally radioactive isotopes.

3.

What are cosmic rays?

High-energy radiation arriving from space.

4.

How can radioactive substances in buildings contribute to background radiation?

Building materials and radon gas can contribute to background radiation indoors.

5.

How does radiation from space reach Earth?

It enters the atmosphere as cosmic radiation and secondary radiation.

6.

Why can the level of background radiation vary between different locations?

The concentration of radioactive materials, altitude and local conditions vary.

6.14 Describe methods for measuring and detecting radioactivity limited to photographic film and a Geiger–Müller tube

1.

How can photographic film be used to detect ionising radiation?

Radiation darkens the film when it exposes the photographic material.

2.

What happens to photographic film when it is exposed to ionising radiation?

It becomes darker after development.

3.

What is a Geiger–Müller tube used to detect?

Ionising radiation.

4.

What does a Geiger–Müller tube produce when ionising radiation enters it?

An electrical pulse, which can be counted.

5.

How can a Geiger counter be used to measure the activity of a radioactive source?

Measure the count rate over a known time, accounting for background radiation.

6.

Why should background radiation be measured when using a Geiger–Müller tube?

So the background count can be subtracted from the measured count rate.

6.15 Recall that an alpha particle is equivalent to a helium nucleus, a beta particle is an electron emitted from the nucleus and a gamma ray is electromagnetic radiation

1.

What is an alpha particle?

A helium nucleus containing two protons and two neutrons.

2.

What particles make up an alpha particle?

2 protons and 2 neutrons.

3.

What is a beta minus particle?

A high-speed electron emitted from the nucleus.

4.

Where does the electron emitted during beta minus decay originate?

It is produced during the transformation of a neutron into a proton.

5.

What type of radiation is a gamma ray?

High-frequency electromagnetic radiation.

6.

How does the composition of an alpha particle differ from that of a beta particle?

An alpha particle contains 2 protons and 2 neutrons; a beta particle is a single electron.

6.16 Compare alpha, beta and gamma radiations in terms of their abilities to penetrate and ionise

1.

Which of alpha, beta and gamma radiation is the most strongly ionising?

Alpha radiation.

2.

Which of alpha, beta and gamma radiation is the most penetrating?

Gamma radiation.

3.

What material can be used to stop alpha radiation?

Paper or a few centimetres of air.

4.

What material can be used to reduce the intensity of beta radiation?

A thin sheet of aluminium.

5.

Why can gamma radiation penetrate much further than alpha radiation?

It is uncharged electromagnetic radiation with much greater penetrating power.

6.

How are the ionising and penetrating abilities of alpha, beta and gamma radiation related?

More strongly ionising radiation is generally less penetrating, and vice versa.

6.17 Describe how and why the atomic model has changed over time including reference to the plum pudding model and Rutherford alpha particle scattering leading to the Bohr model

1.

What did the plum pudding model propose about the structure of an atom?

It was a sphere of positive charge with electrons embedded throughout it.

2.

What did Rutherford's alpha particle scattering experiment provide evidence for?

A small, dense, positively charged nucleus.

3.

What did Rutherford's model propose about the nucleus?

That most of the atom is empty space surrounding a small positive nucleus.

4.

What observation from Rutherford's experiment showed that the nucleus was very small?

A small fraction of alpha particles were deflected through very large angles.

5.

What did Bohr add to the nuclear model of the atom?

That electrons occupy specific fixed energy levels around the nucleus.

6.

Why did experimental evidence cause scientists to change the atomic model?

The evidence contradicted earlier models and supported more accurate explanations.

6.18 Describe the process of β− decay (a neutron becomes a proton plus an electron)

1.

What happens to a neutron during beta minus decay?

It changes into a proton.

2.

What particle is emitted during beta minus decay?

An electron.

3.

What happens to the number of protons during beta minus decay?

It increases by 1.

4.

What happens to the number of neutrons during beta minus decay?

It decreases by 1.

5.

What happens to the mass number during beta minus decay?

It does not change.

6.

What happens to the atomic number during beta minus decay?

It increases by 1.

6.19 Describe the process of β+ decay (a proton becomes a neutron plus a positron)

1.

What happens to a proton during beta plus decay?

It changes into a neutron.

2.

What particle is emitted during beta plus decay?

A positron.

3.

What happens to the number of protons during beta plus decay?

It decreases by 1.

4.

What happens to the number of neutrons during beta plus decay?

It increases by 1.

5.

What happens to the mass number during beta plus decay?

It does not change.

6.

What happens to the atomic number during beta plus decay?

It decreases by 1.

6.20 Explain the effects on the atomic (proton) number and mass (nucleon) number of radioactive decays (α, β, γ and neutron emission)

1.

What happens to the atomic number and mass number during alpha decay?

Atomic number decreases by 2, mass number decreases by 4.

2.

What happens to the atomic number and mass number during beta minus decay?

Atomic number increases by 1, mass number unchanged.

3.

What happens to the atomic number and mass number during beta plus decay?

Atomic number decreases by 1, mass number unchanged.

4.

What happens to the atomic number and mass number during gamma emission?

Neither changes.

5.

What happens to the mass number when a neutron is emitted from a nucleus?

It decreases by 1.

6.

What happens to the atomic number when a neutron is emitted from a nucleus?

It is unchanged, because a neutron has no proton.

6.21 Recall that nuclei that have undergone radioactive decay often undergo nuclear rearrangement with a loss of energy as gamma radiation

1.

What can happen to a nucleus after radioactive decay?

It may rearrange itself into a lower-energy state.

2.

What is meant by nuclear rearrangement?

A change in the arrangement or energy state of particles within the nucleus.

3.

What type of radiation can be emitted when an excited nucleus loses energy?

Gamma radiation.

4.

What happens to the energy of a nucleus when gamma radiation is emitted?

It decreases.

5.

Does gamma emission change the number of protons in the nucleus?

No.

6.

Does gamma emission change the mass number of the nucleus?

No.

6.22 Use given data to balance nuclear equations in terms of mass and charge

1.

What must be conserved when balancing a nuclear equation?

Mass number and atomic number (charge).

2.

What happens to the mass number during alpha decay?

It decreases by 4.

3.

What happens to the atomic number during beta minus decay?

It increases by 1.

4.

Complete the nuclear equation: ²³⁸₉₂U → ²³⁴₉₀Th + ?

⁴₂He.

5.

Complete the nuclear equation: ¹⁴₆C → ¹⁴₇N + ?

⁰₋₁e.

6.

Complete the nuclear equation: ²²₁₁Na → ²²₁₀Ne + ?

⁰₊₁e.

6.23 Describe how the activity of a radioactive source decreases over a period of time

1.

What happens to the activity of a radioactive source over time?

It decreases.

2.

Why does the activity of a radioactive source decrease?

The number of undecayed unstable nuclei decreases.

3.

What happens to the number of undecayed nuclei as time passes?

It decreases continuously as nuclei decay.

4.

What type of curve is produced when activity is plotted against time for radioactive decay?

A decreasing exponential curve.

5.

Does radioactive activity decrease at a constant rate?

No.

6.

How is the decrease in activity related to the number of radioactive nuclei remaining?

Activity is proportional to the number of undecayed nuclei remaining.

6.24 Recall that the unit of activity of a radioactive isotope is the Becquerel, Bq

1.

What is the SI unit of radioactive activity?

The becquerel.

2.

What symbol is used for the Becquerel?

Bq.

3.

What does one Becquerel represent?

One radioactive decay per second.

4.

What does an activity of 500 Bq mean?

500 nuclei decay per second on average.

5.

Which source has the greater activity: 200 Bq or 800 Bq?

800 Bq.

6.

What does a higher activity indicate about the rate of radioactive decay?

A greater rate of decay.

6.25 Explain that the half-life of a radioactive isotope is the time taken for half the undecayed nuclei to decay or the activity of a source to decay by half

1.

What is meant by the half-life of a radioactive isotope?

The time taken for half the undecayed nuclei to decay, or for its activity to fall to half its original value.

2.

How can half-life be determined from a graph of activity against time?

Find an activity value, calculate half of it, and read the time taken to reach that half-value.

3.

What happens to the activity of a source after one half-life?

It becomes half its original value.

4.

What fraction of the original undecayed nuclei remains after one half-life?

One-half.

5.

A radioactive source has an activity of 800 Bq. What is its activity after one half-life?

800 ÷ 2 = 400 Bq.

6.

Why does the half-life remain constant for a particular radioactive isotope?

The probability of decay for each nucleus is constant.

6.26 Explain that it cannot be predicted when a particular nucleus will decay but half-life enables the activity of a very large number of nuclei to be predicted during the decay process

1.

Can the exact time at which a particular unstable nucleus decays be predicted?

No.

2.

Why is radioactive decay described as random?

Each nucleus has a constant probability of decaying at any time, but its actual decay time is unpredictable.

3.

What does half-life allow scientists to predict?

The average behaviour of a large number of nuclei and the activity of a sample.

4.

Why can the behaviour of a large number of radioactive nuclei be predicted even though individual decays are random?

Random individual variations average out, producing predictable statistical behaviour.

5.

How does half-life help predict the activity of a radioactive sample?

The activity can be repeatedly halved over successive half-lives.

6.

Why are predictions based on half-life more reliable for larger samples?

Statistical fluctuations are relatively smaller in larger samples.

6.27 Use the concept of half-life to carry out simple calculations on the decay of a radioactive isotope, including graphical representations

1.

A radioactive source has an activity of 640 Bq. What will its activity be after one half-life?

640 ÷ 2 = 320 Bq.

2.

A source has an activity of 800 Bq and a half-life of 5 years. What will its activity be after 15 years?

15 ÷ 5 = 3 half-lives: 800 → 400 → 200 → 100 Bq.

3.

A radioactive sample has 1,600 undecayed nuclei. How many remain after three half-lives?

1600 → 800 → 400 → 200 nuclei.

4.

A radioactive source decreases from 1,200 Bq to 150 Bq. How many half-lives have elapsed?

1200→600→300→150 is 3 half-lives.

5.

A source has a half-life of 4 hours. How long will it take for its activity to decrease from 400 Bq to 50 Bq?

400→200→100→50 is 3 half-lives, so 3 × 4 = 12 hours.

6.

How can the half-life of a radioactive isotope be determined from an activity-time graph?

Choose an activity value, find half of it, and determine the time difference between the two values.

6.28P Describe uses of radioactivity, including: a household fire (smoke) alarms b irradiating food c sterilisation of equipment d tracing and gauging thicknesses e diagnosis and treatment of cancer

1.

How is radioactivity used in household smoke alarms?

A small alpha source ionises air; smoke reduces the ionisation and changes the current, triggering the alarm.

2.

How can radioactive radiation be used to irradiate food?

Ionising radiation kills microorganisms and insects and slows spoilage without significantly heating the food.

3.

How can radioactivity be used to sterilise medical equipment?

Gamma radiation kills microorganisms.

4.

How can radioactive sources be used to measure or gauge the thickness of materials?

The amount of radiation reaching a detector changes when the thickness changes.

5.

How can radioactive tracers be used in medicine?

They can be introduced into the body and detected to follow the movement or function of substances in organs.

6.

How can radioactivity be used in the diagnosis and treatment of cancer?

Radiation can destroy cancer cells, while tracers can help diagnose cancer.

6.29 Describe the dangers of ionising radiation in terms of tissue damage and possible mutations and relate this to the precautions needed

1.

How can ionising radiation damage living tissue?

By ionising atoms and molecules and breaking chemical bonds.

2.

How can ionising radiation cause mutations?

By damaging or altering DNA.

3.

Why can mutations caused by ionising radiation be harmful?

They may cause abnormal cell function or uncontrolled cell division, potentially leading to cancer.

4.

Why should exposure to ionising radiation be kept as low as reasonably possible?

To reduce the risk of tissue damage and mutations.

5.

What precautions can reduce exposure to ionising radiation?

Reducing exposure time, increasing distance, using shielding and handling sources remotely.

6.

How does reducing exposure time reduce the risk from ionising radiation?

It reduces the number of radiation interactions with the body.

6.30P Explain how the dangers of ionising radiation depend on half-life and relate this to the precautions needed

1.

How does the half-life of a radioactive source affect the duration of its hazard?

A longer half-life means the material remains radioactive for longer.

2.

Why can a long-half-life source remain hazardous for a long period?

It decays slowly, so significant activity can remain for a long time.

3.

Why can a short-half-life source have a high activity initially?

Many nuclei decay rapidly in a short period.

4.

How does the half-life of a source affect decisions about handling and storage?

It determines how long precautions may be required.

5.

Why might a radioactive source with a long half-life require long-term precautions?

It may require secure storage and monitoring for many years.

6.

How can knowledge of half-life help determine appropriate safety precautions?

It helps determine how long the source must be shielded, isolated, monitored and stored.

6.31 Explain the precautions taken to ensure the safety of people exposed to radiation, including limiting the dose for patients and the risks to medical personnel

1.

Why must exposure to ionising radiation be limited?

It can damage tissue and cause mutations.

2.

How can exposure time be reduced when working with radioactive sources?

By planning procedures efficiently and spending as little time as possible near the source.

3.

How can distance from a radioactive source reduce exposure?

Radiation intensity generally decreases with distance.

4.

How can shielding reduce exposure to ionising radiation?

Materials such as lead or concrete absorb or reduce radiation before it reaches people.

5.

Why must medical patients receive only the necessary radiation dose?

Because radiation exposure carries a risk of tissue damage and mutations.

6.

Why are medical personnel particularly careful to minimise repeated exposure to ionising radiation?

They may receive repeated exposure over time.

6.32 Describe the differences between contamination and irradiation effects and compare the hazards associated with these two

1.

What is meant by radioactive contamination?

Radioactive material getting onto or inside a person or object.

2.

What is meant by irradiation?

Exposure to radiation from a source without necessarily receiving radioactive material.

3.

What is the difference between contamination and irradiation?

Contamination involves the material being present; irradiation is exposure without the material being transferred.

4.

Why can contamination continue to expose a person after they leave the source?

The radioactive material remains on or inside the body until removed or decayed.

5.

Why does irradiation not necessarily leave radioactive material on a person?

The person has simply been exposed to radiation.

6.

Which can be particularly difficult to remove: contamination or irradiation?

Contamination, especially when material has entered the body.

6.33P Compare and contrast the treatment of tumours using radiation applied internally or externally

1.

How can radiation be used to treat a tumour externally?

High-energy radiation from a source outside the body is directed towards the tumour.

2.

How can radiation be applied internally to treat a tumour?

A radioactive source is placed inside or close to the tumour.

3.

What is the advantage of directing radiation externally at a tumour?

The beam can be carefully directed and adjusted from outside.

4.

What is the advantage of placing a radioactive source close to or inside a tumour?

A high dose can be delivered to the tumour while reducing exposure to some surrounding tissue.

5.

Why is it important to minimise radiation exposure to healthy tissue during cancer treatment?

Ionising radiation can damage normal cells as well as cancer cells.

6.

What is the main difference between internal and external radiotherapy?

External delivers radiation from outside the body; internal places the source within or close to the tumour.

6.34P Explain some of the uses of radioactive substances in diagnosis of medical conditions, including PET scanners and tracers

1.

What is a radioactive tracer?

A small amount of radioactive substance introduced into the body so its movement can be detected.

2.

Why are radioactive tracers useful in medical diagnosis?

Their radiation can be detected from outside the body, allowing observation of biological processes.

3.

What does a PET scanner detect?

Gamma photons produced following positron annihilation.

4.

Why are radioactive substances used in PET scans?

Positron-emitting tracers produce detectable radiation for imaging.

5.

How can radioactive tracers show the function of organs or tissues?

They accumulate in or move through particular biological processes.

6.

Why must the radioactive substance used as a tracer be carefully selected?

It needs a suitable half-life, appropriate biological behaviour and suitable radiation while minimising dose.

6.35P Explain why isotopes used in PET scanners have to be produced nearby

1.

Why do PET isotopes need to be produced close to where they are used?

Many have very short half-lives.

2.

How does the half-life of a PET isotope affect its transportation?

A short half-life means the activity falls rapidly during transportation.

3.

What happens to the activity of a PET isotope while it is being transported?

It decreases as radioactive nuclei decay.

4.

Why would a very long transport time be unsuitable for many PET isotopes?

Much of the isotope could decay, leaving insufficient activity for a useful scan.

5.

Why must PET isotopes be produced shortly before they are needed?

So sufficient activity remains at the time of use.

6.

How does radioactive decay limit the useful lifetime of isotopes used in PET scanners?

Activity falls exponentially with time, making the isotope less effective as a tracer.

6.36P Evaluate the advantages and disadvantages of nuclear power for generating electricity, including the lack of carbon dioxide emissions, risks, public perception, waste disposal and safety issues

1.

What is one advantage of nuclear power in terms of carbon dioxide emissions during electricity generation?

It produces very little carbon dioxide, helping reduce greenhouse gas emissions.

2.

What is one disadvantage of nuclear power related to radioactive waste?

It remains hazardous and requires careful storage and long-term management.

3.

What safety risks are associated with nuclear power stations?

Radiation exposure and the possibility of serious accidents.

4.

How can public perception affect the development of nuclear power?

Concerns about accidents, radiation and waste can influence planning and acceptance.

5.

Why does nuclear waste require careful long-term management?

Some radioactive materials have long half-lives and remain hazardous for extended periods.

6.

How can nuclear power be evaluated against fossil fuels and renewable energy sources?

It provides reliable low-carbon electricity but has construction costs, waste and accident risks to weigh against alternatives.

6.37P Recall that nuclear reactions, including fission, fusion and radioactive decay, can be a source of energy

1.

What is nuclear fission?

The splitting of a large atomic nucleus into smaller nuclei, releasing energy.

2.

What is nuclear fusion?

The joining of smaller nuclei to form a larger nucleus, releasing energy.

3.

How can radioactive decay release energy?

An unstable nucleus changes into a more stable, lower-energy configuration.

4.

Which nuclear process powers stars?

Nuclear fusion.

5.

Which nuclear process is used in current nuclear power stations?

Nuclear fission.

6.

Why can changes in atomic nuclei release large amounts of energy?

Changes in nuclear binding involve very large energy changes associated with small differences in mass.

6.38P Explain how the fission of U-235 produces two daughter nuclei and the emission of two or more neutrons, accompanied by a release of energy

1.

What happens to a U-235 nucleus during fission?

It absorbs a neutron, becomes unstable and splits into two smaller daughter nuclei.

2.

What causes a U-235 nucleus to undergo fission in a nuclear reactor?

Absorbing a neutron.

3.

What is produced when a U-235 nucleus undergoes fission?

Two daughter nuclei, two or more neutrons, and energy.

4.

How many neutrons are typically emitted during the fission of U-235?

Typically two or three.

5.

Why is energy released during nuclear fission?

The total mass of the products is slightly less than the mass of the original system, and the difference is converted to energy.

6.

How can the emitted neutrons lead to further fission reactions?

They can be absorbed by other U-235 nuclei, causing further fission.

6.39P Explain the principle of a controlled nuclear chain reaction

1.

What is a nuclear chain reaction?

A process in which neutrons released by one fission cause further fissions.

2.

How can one fission reaction lead to further fission reactions?

The neutrons released can cause other U-235 nuclei to undergo fission.

3.

What role do neutrons play in a nuclear chain reaction?

They initiate and sustain successive fission reactions.

4.

What is meant by a controlled chain reaction?

One in which the number of fissions per unit time is regulated.

5.

Why must the rate of fission be controlled in a nuclear reactor?

To maintain a steady energy output and prevent the reaction increasing too rapidly.

6.

What could happen if a chain reaction were not properly controlled?

It could increase rapidly, causing a large and potentially dangerous release of energy.

6.40P Explain how the chain reaction is controlled in a nuclear reactor, including the action of moderators and control rods

1.

What is the purpose of a moderator in a nuclear reactor?

To slow down neutrons released during fission.

2.

How does a moderator affect the speed of neutrons?

It reduces their speed through collisions with nuclei in the moderator material.

3.

What is the purpose of control rods?

To absorb neutrons.

4.

How do control rods control the rate of the nuclear chain reaction?

By reducing the number of neutrons available to cause further fission.

5.

What happens to the chain reaction when control rods are inserted further into the reactor?

It slows down.

6.

Why must the moderator and control rods work together to control the reaction?

The moderator produces neutrons of an appropriate speed, while control rods regulate their number, allowing a controlled rate.

6.41P Describe how thermal (heat) energy from the chain reaction is used in the generation of electricity in a nuclear power station

1.

What form of energy is released by the nuclear chain reaction?

Thermal energy.

2.

How is thermal energy transferred from the reactor to water or another coolant?

By heating in the reactor.

3.

How is steam produced in a nuclear power station?

The heated water produces steam, directly or via a heat exchanger.

4.

What does the steam cause to rotate?

A turbine.

5.

How does a turbine generate mechanical energy?

The rotating turbine has mechanical energy from the steam.

6.

How is the turbine's mechanical energy converted into electrical energy?

The turbine drives a generator.

6.42P Recall that the products of nuclear fission are radioactive

1.

What happens to the daughter nuclei produced by nuclear fission?

They are often radioactive and undergo further decay.

2.

Why are many fission products radioactive?

The daughter nuclei have unstable combinations of protons and neutrons.

3.

Why do radioactive fission products require careful handling?

They can emit ionising radiation.

4.

What type of radiation can radioactive fission products emit?

Alpha, beta and gamma radiation, depending on the isotope.

5.

Why must radioactive fission waste be stored safely?

To prevent radiation exposure and contamination.

6.

How does the radioactivity of fission products change over time?

It generally decreases as unstable nuclei decay.

6.43P Describe nuclear fusion as the creation of larger nuclei resulting in a loss of mass from smaller nuclei, accompanied by a release of energy, and recognise fusion as the energy source for stars

1.

What is nuclear fusion?

The joining of smaller atomic nuclei to form a larger nucleus.

2.

What happens to smaller nuclei during fusion?

They combine to form a larger nucleus, releasing energy.

3.

Why is mass lost during nuclear fusion?

The mass of the products is slightly less than the combined mass of the original nuclei.

4.

How is the lost mass related to the energy released?

It is converted into energy according to E = mc².

5.

Why is nuclear fusion the energy source of stars?

Hydrogen nuclei combine through fusion, releasing enormous amounts of energy.

6.

What happens to the nuclei and energy during fusion in the core of a star?

High temperature and pressure allow nuclei to fuse, producing larger nuclei and releasing energy.

6.44P Explain the difference between nuclear fusion and nuclear fission

1.

What is the main difference between nuclear fission and nuclear fusion?

Fission splits a large nucleus, whereas fusion joins smaller nuclei.

2.

What happens to a large nucleus during fission?

It breaks into two or more smaller nuclei.

3.

What happens to smaller nuclei during fusion?

They combine to form a larger nucleus.

4.

Which process produces daughter nuclei from a larger nucleus?

Fission.

5.

Which process combines smaller nuclei to form a larger nucleus?

Fusion.

6.

Why can both fission and fusion release energy?

The products have greater nuclear stability and a lower total mass, with the mass difference converted into energy.

6.45P Explain why nuclear fusion does not happen at low temperatures and pressures, due to electrostatic repulsion of protons

1.

Why do positively charged nuclei repel each other?

Like electric charges repel.

2.

What is electrostatic repulsion?

The force that pushes positively charged nuclei apart.

3.

Why must nuclei have very high kinetic energies for fusion to occur?

To get close enough for the strong nuclear force to overcome electrostatic repulsion.

4.

How does increasing temperature help nuclei overcome electrostatic repulsion?

It increases the particles' average kinetic energy.

5.

Why is high pressure useful for nuclear fusion?

It forces nuclei closer together, increasing the likelihood of collisions and fusion.

6.

Why does nuclear fusion not normally occur at low temperatures and pressures?

Nuclei generally do not have enough energy or proximity to overcome electrostatic repulsion.

6.46P Relate the conditions for fusion to the difficulty of making a practical and economic form of power station

1.

Why must extremely high temperatures be achieved for controlled fusion?

To give nuclei enough kinetic energy to overcome electrostatic repulsion.

2.

Why is maintaining the conditions required for fusion technically difficult?

Maintaining extreme temperatures, pressures and plasma conditions requires advanced equipment.

3.

Why must a fusion reactor keep the hot plasma away from the reactor walls?

The extremely high temperature could damage or melt the materials.

4.

Why is producing more energy than is required to sustain fusion important for a practical power station?

A practical power station must produce more usable energy than is required to heat, confine and sustain the reaction.

5.

Why does the difficulty of maintaining fusion conditions affect the economic viability of fusion power?

It increases complexity, cost and engineering demands.

6.

What makes developing a practical fusion power station more difficult than simply achieving fusion?

The reaction must be sustained reliably, safely and economically while producing a useful net energy output.

7.1P Explain how and why both the weight of any body and the value of g differ between the surface of the Earth and the surface of other bodies in space, including the Moon

1.

What determines the weight of an object on the surface of a celestial body?

Its mass and the gravitational field strength of the celestial body: W = m × g.

2.

What determines the value of gravitational field strength, g, at the surface of a celestial body?

Mainly the mass and radius of the celestial body.

3.

Why is an object's weight different on the Moon compared with Earth?

The Moon has a weaker gravitational field than Earth.

4.

What happens to an object's mass when it is moved from Earth to the Moon?

It does not change.

5.

An object has a mass of 6 kg on the Moon where g = 1.6 N/kg. What is its weight?

W = 6 × 1.6 = 9.6 N.

6.

Why is the value of g different on different planets and moons?

Celestial bodies have different masses and sizes, producing different gravitational fields.

7.2P Recall that our Solar System consists of the Sun (our star), eight planets and their natural satellites (such as our Moon); dwarf planets; asteroids and comets

1.

What is at the centre of our Solar System?

The Sun.

2.

How many planets are in our Solar System?

Eight.

3.

What is a natural satellite?

A naturally occurring object that orbits a planet or other larger body, such as the Moon orbiting Earth.

4.

What is a dwarf planet?

A roughly spherical object that orbits the Sun but has not cleared its orbital region of other objects.

5.

What are asteroids?

Rocky objects that orbit the Sun.

6.

What are comets?

Bodies made mainly of ice and dust that orbit the Sun, often in elongated orbits.

7.3P Recall the names and order, in terms of distance from the Sun, of the eight planets

1.

What is the closest planet to the Sun?

Mercury.

2.

What is the second planet from the Sun?

Venus.

3.

What is the third planet from the Sun?

Earth.

4.

What is the fourth planet from the Sun?

Mars.

5.

What is the fifth planet from the Sun?

Jupiter.

6.

What are the eight planets in order of increasing distance from the Sun?

Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

7.4P Describe how ideas about the structure of the Solar System have changed over time

1.

What did the geocentric model propose about the structure of the Solar System?

That Earth was at the centre and the Sun and planets moved around it.

2.

What did the heliocentric model propose about the structure of the Solar System?

That the Sun is at the centre and the planets orbit the Sun.

3.

Who is associated with the development of the heliocentric model?

Nicolaus Copernicus.

4.

What is the main difference between the geocentric and heliocentric models?

The geocentric model places Earth at the centre; the heliocentric model places the Sun at the centre.

5.

How did observations of planets contribute to changes in models of the Solar System?

They provided evidence that improved models of the Solar System.

6.

Why can scientific models of the Solar System change over time?

New experimental or observational evidence can show that an existing model is incomplete or incorrect.

7.5P Describe the orbits of moons, planets, comets and artificial satellites

1.

What causes moons and planets to remain in orbit?

Gravity.

2.

What type of path does a planet follow around the Sun?

An approximately elliptical orbit.

3.

What type of object is a moon orbiting?

A planet or other larger body.

4.

What type of orbit can an artificial satellite have around Earth?

An elliptical or approximately circular orbit.

5.

How does a comet's orbit differ from the nearly circular orbits of many planets?

A comet usually follows a highly elongated elliptical orbit.

6.

Why does an object in orbit continually change direction?

The gravitational force acts towards the central body.

7.6P Explain for circular orbits how the force of gravity can lead to changing velocity of a planet but unchanged speed

1.

What force keeps a planet in a circular orbit around the Sun?

Gravity.

2.

In which direction does the gravitational force act on an orbiting planet?

Towards the centre of the orbit.

3.

Why does the velocity of a planet change during a circular orbit?

Velocity includes both speed and direction, and the direction continually changes.

4.

Why can the speed of a planet remain constant during a circular orbit?

The gravitational force acts perpendicular to the instantaneous direction of motion.

5.

What component of velocity changes during uniform circular motion?

The direction.

6.

Why is an object moving at constant speed around a circle still accelerating?

Its velocity is continually changing direction.

7.7P Explain how, for a stable orbit, the radius must change if orbital speed changes (qualitative only)

1.

What happens to the radius of a stable circular orbit when orbital speed increases?

It decreases.

2.

What happens to the radius of a stable circular orbit when orbital speed decreases?

It increases.

3.

Why must orbital radius change when orbital speed changes?

The gravitational force available to provide the centripetal force depends on distance from the central body.

4.

What happens to the gravitational force as an orbiting object's distance from the central body increases?

It decreases.

5.

For a stable orbit, why cannot orbital speed and radius change independently?

Both determine the centripetal force needed for a stable orbit.

6.

How does a higher orbital speed relate qualitatively to the radius of a stable orbit?

A higher orbital speed corresponds to a smaller stable orbital radius.

7.8P Compare the Steady State and Big Bang theories

1.

What does the Big Bang theory propose about the origin of the Universe?

That it began in an extremely hot, dense state and has expanded over time.

2.

What does the Steady State theory propose about the Universe?

That it has always existed and, although expanding, its overall appearance remains constant with new matter continuously created.

3.

How does the Big Bang theory describe the density of the Universe over time?

It was much hotter and denser in the past and has become less dense as it expanded.

4.

How does the Steady State theory differ from the Big Bang theory regarding the age of the Universe?

It proposes an eternal Universe with no unique beginning.

5.

What is one major difference between the Big Bang and Steady State theories?

The Big Bang describes an evolving Universe with a hot, dense beginning; the Steady State describes an eternal Universe with a constant appearance.

6.

Which theory proposes that the Universe has changed significantly from a much hotter, denser early state?

The Big Bang theory.

7.9P Describe evidence supporting the Big Bang theory, limited to red-shift and the cosmic microwave background (CMB) radiation

1.

What is red-shift?

The increase in the observed wavelength of light from an object moving away from an observer.

2.

How does red-shift provide evidence that the Universe is expanding?

Many galaxies show red-shift, showing they are generally moving away from Earth.

3.

What is cosmic microwave background radiation?

Weak microwave radiation detected throughout the Universe.

4.

Why is the CMB considered evidence for the Big Bang theory?

It is radiation left over from the hot, dense early Universe.

5.

What does the existence of the CMB suggest about the early Universe?

It was much hotter and denser than it is today.

6.

How do red-shift and CMB radiation together support the Big Bang theory?

Red-shift shows expansion, while the CMB shows a hot, dense early Universe; together they strongly support the theory.

7.10P Recall that as there is more evidence supporting the Big Bang theory than the Steady State theory, it is the currently accepted model for the origin of the Universe

1.

Which theory is currently the accepted model for the origin of the Universe?

The Big Bang theory.

2.

Why is the Big Bang theory currently accepted?

There is more supporting evidence for it than for the Steady State theory.

3.

What evidence supports the Big Bang theory?

Red-shift of galaxies and cosmic microwave background radiation.

4.

Why is the Steady State theory no longer the accepted model?

It does not explain the evidence as successfully as the Big Bang theory.

5.

How does scientific evidence affect the acceptance of theories?

It can cause theories to become accepted, rejected or modified.

6.

What does it mean to say that the Big Bang theory is the currently accepted model?

It provides the best-supported scientific explanation of the origin and evolution of the Universe.

7.11P Describe that if a wave source is moving relative to an observer there will be a change in the observed frequency and wavelength

1.

What happens to the observed frequency when a wave source moves towards an observer?

It increases.

2.

What happens to the observed frequency when a wave source moves away from an observer?

It decreases.

3.

What happens to the observed wavelength when a source moves towards an observer?

It decreases.

4.

What happens to the observed wavelength when a source moves away from an observer?

It increases.

5.

What is the relationship between the motion of a source and the observed frequency?

The relative motion of source and observer changes the frequency and wavelength measured.

6.

What is the name of the effect in which the observed frequency changes because of relative motion between a source and observer?

The Doppler effect.

7.12P Describe the red-shift in light received from galaxies at different distances away from the Earth

1.

What is meant by red-shift?

The increase in observed wavelength of light from a source moving away from the observer.

2.

What happens to the observed wavelength of light from a red-shifted galaxy?

It is increased.

3.

How does the amount of red-shift vary with the distance of a galaxy from Earth?

More distant galaxies generally show greater red-shifts.

4.

What does a greater red-shift indicate about a distant galaxy's motion relative to Earth?

It is moving away at a greater speed.

5.

Why does light from distant galaxies often appear red-shifted?

The galaxies are moving away as the Universe expands.

6.

How can the red-shift of light from galaxies be used to investigate their motion?

Measuring red-shift allows recession speeds to be estimated.

7.13P Explain why the red-shift of galaxies provides evidence for the Universe expanding

1.

What does the red-shift of light from galaxies indicate about their motion?

That galaxies are generally moving away from Earth.

2.

Why does the red-shift of distant galaxies provide evidence that they are moving away from Earth?

Light from a moving-away galaxy has an increased observed wavelength.

3.

What does the widespread red-shift of galaxies suggest about the Universe?

That space is expanding and galaxies are generally moving apart.

4.

How does the relationship between galaxy distance and red-shift support an expanding Universe?

Greater red-shift of more distant galaxies supports the expected relationship for an expanding Universe.

5.

Why would observations of red-shift be difficult to explain if the Universe were completely static?

A static Universe would not naturally explain the widespread pattern of galaxy red-shifts.

6.

How does galaxy red-shift provide evidence for expansion rather than simply the motion of one galaxy?

The red-shift of many galaxies across different directions supports overall expansion.

7.14P Explain how both the Big Bang and Steady State theories of the origin of the Universe both account for red-shift of galaxies

1.

How does the Big Bang theory explain the red-shift of distant galaxies?

As evidence that the Universe has expanded from an earlier, hotter and denser state.

2.

How does the Steady State theory account for the red-shift of galaxies?

It also allows an expanding Universe, so it can account for the observed red-shift.

3.

What observation can both the Big Bang and Steady State theories explain?

That distant galaxies are generally red-shifted.

4.

Why does red-shift alone not distinguish completely between the Big Bang and Steady State theories?

Both can account for an expanding Universe.

5.

What additional evidence supports the Big Bang theory over the Steady State theory?

The cosmic microwave background radiation.

6.

How do the two theories differ in their explanation of the overall evolution of the Universe despite both accounting for galaxy red-shift?

The Big Bang describes an evolved Universe from a hot, dense beginning; the Steady State proposes an eternal, constant Universe.

7.15P Explain how the discovery of the CMB radiation led to the Big Bang theory becoming the currently accepted model

1.

What is the CMB?

Weak microwave radiation detected throughout the Universe.

2.

Why was the discovery of CMB radiation important to cosmology?

It provided important evidence about the conditions of the early Universe.

3.

What does the CMB provide evidence for about the early Universe?

That it was very hot and dense.

4.

Why does the CMB support the Big Bang theory more strongly than the Steady State theory?

The Steady State theory does not naturally predict this relic radiation from a hot, dense beginning.

5.

How did the discovery of CMB radiation affect scientific views about the origin of the Universe?

It caused scientists to favour the Big Bang model.

6.

Why did evidence from the CMB contribute to the Big Bang theory becoming the accepted model?

Together with galaxy red-shift, it provided strong supporting evidence.

7.16P Describe the evolution of stars of similar mass to the Sun through the following stages: a nebula b star (main sequence) c red giant d white dwarf

1.

What is a nebula?

A large cloud of gas and dust in space.

2.

What happens to a nebula as a star similar in mass to the Sun begins to form?

Gravity causes material to come together and form a protostar, which develops into a star.

3.

What is the main-sequence stage of a star?

A stable stage in which nuclear fusion provides energy while gravity is balanced by outward pressure.

4.

What happens to a Sun-like star after it leaves the main sequence?

It expands and becomes a red giant.

5.

What happens to a red giant eventually to form a white dwarf?

The outer layers are lost, leaving behind a hot, dense white dwarf.

6.

What is the correct sequence of stages for a star with a mass similar to the Sun?

Nebula → main-sequence star → red giant → white dwarf.

7.17P Explain how the balance between thermal expansion and gravity affects the life cycle of stars

1.

What force tends to make a star contract under gravity?

Its own gravity.

2.

What causes thermal pressure or expansion within a star?

Energy released by nuclear fusion.

3.

What happens when gravity and thermal expansion are balanced in a stable star?

The star remains stable.

4.

What happens to a star if gravity becomes greater than the outward thermal pressure?

It contracts.

5.

What happens when the balance between gravity and thermal expansion changes as a star evolves?

The star changes size and evolves.

6.

How does the balance between gravity and thermal expansion influence the life cycle of a star?

It controls the stability and changes that occur during the star's life cycle.

7.18P Describe the evolution of stars with a mass larger than the Sun

1.

How does the evolution of a massive star initially differ from that of a Sun-like star?

It uses its nuclear fuel more rapidly than a Sun-like star.

2.

What happens to a massive star after its main-sequence stage?

It becomes a red supergiant and undergoes further nuclear fusion reactions.

3.

What is a supernova?

A powerful explosion in which a massive star's outer layers are violently expelled.

4.

What can remain after a massive star undergoes a supernova?

A neutron star or a black hole.

5.

How can a massive star eventually form a neutron star?

The core collapses and becomes extremely dense.

6.

Under what conditions can the remnant of a massive star become a black hole?

If the remaining core is sufficiently massive, its gravity causes it to collapse further.

7.19P Describe how methods of observing the Universe have changed over time including why some telescopes are located outside the Earth's atmosphere

1.

How have methods of observing the Universe changed over time?

From naked-eye observations to increasingly powerful ground-based and space-based telescopes.

2.

Why are modern telescopes able to observe more of the electromagnetic spectrum than early optical telescopes?

They can detect many regions of the spectrum, not just visible light.

3.

Why can Earth's atmosphere interfere with astronomical observations?

It can absorb or scatter some electromagnetic radiation and distort visible-light observations.

4.

Why are some telescopes placed above Earth's atmosphere?

To avoid atmospheric absorption, scattering and distortion.

5.

What advantage does a space telescope have over a ground-based telescope?

It can produce clearer observations and detect wavelengths that cannot pass through the atmosphere.

6.

Why are different types of telescope used to observe different regions of the electromagnetic spectrum?

Different wavelengths provide different information about astronomical objects.

8.1 Describe the changes involved in the way energy is stored when systems change

1.

What happens to the energy stores of a system when the system changes?

Energy is transferred between different stores.

2.

What energy store increases when an object is raised?

Its gravitational potential energy store.

3.

What energy store increases when an object speeds up?

Its kinetic energy store.

4.

What energy store decreases when a moving object slows down?

Its kinetic energy store.

5.

How can energy be transferred between different energy stores when a system changes?

Mechanically, electrically, by heating or by radiation.

6.

What happens to the total energy of a closed system during a change?

It remains constant.

8.2 Draw and interpret diagrams to represent energy transfers

1.

What is an energy transfer diagram used to represent?

How energy moves between different energy stores in a system.

2.

How can an energy transfer diagram show the initial and final energy stores of a system?

By showing the stores at the start, the transfers taking place and the stores at the end.

3.

What does the width of an arrow represent in an energy transfer diagram?

The relative amount of energy being transferred.

4.

How can an energy transfer diagram show that some energy has been dissipated?

As energy transferred to the thermal energy store of the surroundings.

5.

Draw an energy transfer diagram for a battery powering an electric motor.

Chemical energy store → electrical transfer → kinetic energy store + thermal energy store.

6.

Interpret an energy transfer diagram showing chemical energy transferred into kinetic energy and thermal energy.

The chemical energy store decreases while kinetic and thermal energy stores increase.

8.3 Explain that where there are energy transfers in a closed system there is no net change to the total energy in that system

1.

What is meant by a closed system?

A system in which energy cannot enter or leave.

2.

What happens to the total energy of a closed system when energy is transferred between stores?

It remains constant.

3.

Why is energy not destroyed during an energy transfer?

It is transferred between stores or to the surroundings, not destroyed.

4.

If 500 J of energy is transferred from one energy store to another in a closed system, how much total energy is lost?

0 J.

5.

A closed system initially contains 2,000 J of energy. How much total energy does it contain after internal energy transfers?

2,000 J.

6.

How does conservation of energy apply to a closed system?

The total energy before a change equals the total energy after.

8.4 Identify the different ways that the energy of a system can be changed: a through work done by forces b in electrical equipment c in heating

1.

How can doing work by forces change the energy of a system?

By mechanically transferring energy to or from the system.

2.

How can electrical equipment change the energy of a system?

By transferring energy electrically into different energy stores.

3.

How can heating change the energy of a system?

By transferring energy from a hotter object or source to a cooler system.

4.

What energy transfer occurs when a force accelerates an object?

Energy is transferred to its kinetic energy store.

5.

What energy transfer occurs when an electric heater heats water?

Electrical energy is transferred to the thermal energy store of the water.

6.

What energy transfer occurs when an object is heated by a flame?

Energy is transferred by heating from the flame to the object's thermal energy store.

8.5 Describe how to measure the work done by a force and understand that energy transferred (joule, J) is equal to work done (joule, J)

1.

How can the work done by a force be measured?

By multiplying the force by the distance moved in the direction of the force.

2.

What two quantities are needed to calculate work done by a force?

Force and distance moved in the direction of the force.

3.

What is the unit of work done?

The joule (J).

4.

What is the relationship between work done and energy transferred?

They are equal.

5.

If a force does 250 J of work, how much energy is transferred?

250 J.

6.

Why is work done considered to be an energy transfer?

A force transfers energy when it moves an object through a distance.

8.6 Recall and use the equation: work done (joule, J) = force (newton, N) × distance moved in the direction of the force (metre, m) E = F × d

1.

What equation is used to calculate work done by a force?

E = F × d.

2.

What unit is used for work done in the equation E = F × d?

The joule (J).

3.

A force of 20 N moves an object 5 m in the direction of the force. Calculate the work done.

E = 20 × 5 = 100 J.

4.

A force of 150 N does 600 J of work. Calculate the distance moved.

d = 600 ÷ 150 = 4 m.

5.

An object moves 8 m while a force of 40 N acts in the direction of motion. Calculate the energy transferred.

E = 40 × 8 = 320 J.

6.

A force does 900 J of work while moving an object 3 m. Calculate the force.

F = 900 ÷ 3 = 300 N.

8.7 Describe and calculate the changes in energy involved when a system is changed by work done by forces

1.

How does work done by a force transfer energy to or from a system?

It transfers energy mechanically into or out of the system.

2.

What happens to the kinetic energy of an object when a resultant force accelerates it?

It increases.

3.

What happens to the gravitational potential energy of an object when work is done to raise it?

It increases.

4.

A force of 50 N moves an object 6 m. Calculate the energy transferred by the force.

E = 50 × 6 = 300 J.

5.

A 4 kg object is raised vertically through 5 m where g = 10 N/kg. Calculate the increase in gravitational potential energy.

ΔGPE = 4 × 10 × 5 = 200 J.

6.

A 2 kg object accelerates from rest to 10 m/s. Calculate its increase in kinetic energy.

KE = ½ × 2 × 10² = 100 J.

8.8 Recall and use the equation to calculate the change in gravitational PE when an object is raised above the ground: change in gravitational potential energy (joule, J) = mass (kilogram, kg) × gravitational field strength (newton per kilogram, N/kg) × change in vertical height (metre, m) ∆GPE = m × g × ∆h

1.

What equation is used to calculate a change in gravitational potential energy?

ΔGPE = m × g × Δh.

2.

What happens to gravitational potential energy when an object is raised?

It increases.

3.

Calculate the change in gravitational potential energy of a 5 kg object raised by 4 m when g = 10 N/kg.

ΔGPE = 5 × 10 × 4 = 200 J.

4.

A 2 kg object gains 120 J of gravitational potential energy when raised through 6 m. Calculate g.

g = 120 ÷ (2 × 6) = 10 N/kg.

5.

An object gains 500 J of gravitational potential energy when raised through 5 m where g = 10 N/kg. Calculate its mass.

m = 500 ÷ (10 × 5) = 10 kg.

6.

A 10 kg object is raised through 3 m on a planet where g = 8 N/kg. Calculate its change in gravitational potential energy.

ΔGPE = 10 × 8 × 3 = 240 J.

8.9 Recall and use the equation to calculate the amounts of energy associated with a moving object: kinetic energy (joule, J) = 1/2 × mass (kilogram, kg) × (speed)² ((metre/second)², (m/s)²) KE = 1/2 × m × v²

1.

What equation is used to calculate the kinetic energy of a moving object?

KE = ½ × m × v².

2.

What happens to kinetic energy when the speed of an object increases?

It increases (with the square of speed).

3.

Calculate the kinetic energy of a 4 kg object moving at 5 m/s.

KE = ½ × 4 × 5² = 50 J.

4.

A 2 kg object has a kinetic energy of 100 J. Calculate its speed.

v = √(100 ÷ (½ × 2)) = 10 m/s.

5.

A 10 kg object moves at 8 m/s. Calculate its kinetic energy.

KE = ½ × 10 × 8² = 320 J.

6.

An object's speed doubles. By what factor does its kinetic energy change?

It increases by a factor of 4.

8.10 Explain, using examples, how in all system changes energy is dissipated so that it is stored in less useful ways

1.

What is meant by energy being dissipated?

It is transferred to stores that are less useful for doing useful work.

2.

Why is dissipated energy described as being stored in less useful ways?

It becomes spread out in the surroundings and is harder to transfer into useful forms.

3.

How is energy dissipated when a car brakes?

Friction transfers kinetic energy to the thermal energy stores of the brakes, tyres, road and surroundings.

4.

How is energy dissipated when an object slides across a rough surface?

Friction transfers kinetic energy to thermal energy stores.

5.

How can friction cause energy to be dissipated?

It transfers energy from useful stores into thermal energy stores of the objects and surroundings.

6.

Give an example of a system in which energy is transferred to the thermal energy store of the surroundings.

A bicycle braking.

8.11 Explain that mechanical processes become wasteful when they cause a rise in temperature so dissipating energy in heating the surroundings

1.

Why does friction make a mechanical process less efficient?

It transfers useful mechanical energy to thermal energy.

2.

What happens to energy when friction causes surfaces to heat up?

Mechanical energy is transferred to their thermal energy stores.

3.

Why is heating the surroundings considered a wasteful energy transfer?

The thermal energy is not useful for the intended purpose.

4.

How does friction affect the efficiency of a mechanical system?

It reduces efficiency by dissipating some of the input energy.

5.

What happens to the temperature of surfaces when mechanical energy is dissipated by friction?

It increases.

6.

Why does a rise in temperature indicate that energy has been dissipated in a mechanical process?

It shows energy has been transferred into thermal energy stores.

8.12 Define power as the rate at which energy is transferred and use examples to explain this definition

1.

What is meant by power?

The rate at which energy is transferred.

2.

What does the rate of energy transfer describe?

How much energy is transferred per unit time.

3.

Which transfers energy more quickly: a 1,000 W device or a 500 W device?

The 1,000 W device.

4.

Two machines transfer the same amount of energy, but one does so in less time. Which machine has greater power?

The one that takes less time.

5.

Why does a high-power appliance transfer energy more rapidly than a low-power appliance?

It transfers more energy each second.

6.

How can the power of an electrical appliance be interpreted in terms of energy transferred each second?

A power rating of 1 W means 1 J of energy is transferred every second.

8.13 Recall and use the equation: power (watt, W) = work done (joule, J) ÷ time taken (second, s) P = E ÷ t

1.

What equation is used to calculate power?

P = E ÷ t.

2.

What are the units of power, energy and time in P = E ÷ t?

Watts (W), joules (J) and seconds (s).

3.

A machine transfers 6,000 J of energy in 20 s. Calculate its power.

P = 6000 ÷ 20 = 300 W.

4.

A motor has a power of 500 W and operates for 30 s. Calculate the energy transferred.

E = 500 × 30 = 15,000 J.

5.

A device transfers 12,000 J of energy at a power of 600 W. Calculate the time taken.

t = 12,000 ÷ 600 = 20 s.

6.

A machine does 9,000 J of work in 15 s. Calculate its power.

P = 9000 ÷ 15 = 600 W.

8.14 Recall that one watt is equal to one joule per second, J/s

1.

What is one watt equal to in joules per second?

1 W = 1 J/s.

2.

What does a power rating of 1 W mean?

1 J of energy is transferred every second.

3.

How many joules does a 100 W device transfer each second?

100 J.

4.

How much energy does a 2,000 W device transfer in 1 second?

2,000 J.

5.

A device transfers 500 J every second. What is its power?

500 W.

6.

A 60 W lamp operates for 10 s. How much energy does it transfer?

E = 60 × 10 = 600 J.

8.15 Recall and use the equation: efficiency = useful energy transferred by the device ÷ total energy supplied to the device

1.

What equation is used to calculate efficiency?

Efficiency = useful energy transferred ÷ total energy supplied.

2.

Why is efficiency usually expressed as a value between 0 and 1 or as a percentage?

Because useful energy can never exceed the total energy supplied.

3.

A device receives 500 J of energy and transfers 400 J usefully. Calculate its efficiency.

Efficiency = 400 ÷ 500 = 0.8 = 80%.

4.

A machine has an efficiency of 0.8 and receives 2,000 J of energy. Calculate the useful energy transferred.

Useful energy = 0.8 × 2000 = 1,600 J.

5.

A device transfers 600 J usefully from a total input of 1,000 J. Calculate its efficiency as a percentage.

Efficiency = 600 ÷ 1000 = 60%.

6.

A machine has an efficiency of 75% and receives 4,000 J of energy. Calculate the useful energy transferred.

Useful energy = 0.75 × 4000 = 3,000 J.

9.1 Describe, with examples, how objects can interact a at a distance without contact, linking these to the gravitational, electrostatic and magnetic fields involved b by contact, including normal contact force and friction c producing pairs of forces which can be represented as vectors

1.

What three types of field force can act between objects without physical contact?

Gravitational, electrostatic and magnetic forces.

2.

How does a gravitational field allow two masses to interact at a distance?

It allows masses to attract each other at a distance.

3.

How does an electrostatic field allow charged objects to interact at a distance?

Like charges repel and unlike charges attract.

4.

What are the normal contact force and friction examples of?

Contact forces, acting between objects that are touching.

5.

What happens when two objects interact and produce a pair of forces?

Each object exerts a force on the other, equal in size and opposite in direction.

6.

How can forces acting on interacting objects be represented using vectors?

Using arrows, with direction showing the force's direction and length representing its magnitude.

9.2 Explain the difference between vector and scalar quantities using examples

1.

What is a scalar quantity?

A quantity that has magnitude only.

2.

What is a vector quantity?

A quantity that has both magnitude and direction.

3.

What is the difference between the information given by a scalar and a vector?

A scalar gives size only; a vector gives size and direction.

4.

Is speed a scalar or vector quantity?

A scalar quantity.

5.

Is velocity a scalar or vector quantity?

A vector quantity.

6.

Give one example of a force being represented as a vector.

A force of 10 N to the right can be shown by an arrow pointing right, its length representing 10 N to a chosen scale.

9.3 Use vector diagrams to illustrate resolution of forces, a net force, and equilibrium situations (scale drawings only)

1.

What is meant by the resolution of a force?

Representing one force as two or more component forces acting in different directions.

2.

What is a net force?

The resultant force obtained by combining all the forces acting on an object.

3.

How can a vector diagram show the resultant or net force acting on an object?

By combining the force vectors according to their magnitudes and directions.

4.

What does a vector diagram show when forces are in equilibrium?

The vectors balance so the resultant force is zero.

5.

Two perpendicular forces of 3 N and 4 N act on an object. Using a scale drawing, what is the magnitude of the resultant force?

Resultant = √(3² + 4²) = √25 = 5 N.

6.

How can a scale drawing be used to determine the resultant of two forces?

Draw the vectors to scale, complete the vector triangle or parallelogram, and measure the resultant.

9.4 Draw and use free body force diagrams

1.

What is a free body force diagram?

A diagram showing all the external forces acting on an object using labelled arrows.

2.

What does each arrow represent on a free body force diagram?

One force acting on the object.

3.

How should the direction of an arrow represent a force?

It points in the direction in which the force acts.

4.

What forces would normally be shown on a free body diagram of a falling object?

Weight acting downward and air resistance acting upward.

5.

What would a free body diagram show for an object resting on a horizontal surface?

Weight acting downward and normal contact force acting upward.

6.

How can a free body diagram be used to determine the resultant force on an object?

The forces shown can be combined to determine the resultant force.

9.5 Explain examples of the forces acting on an isolated solid object or a system where several forces lead to a resultant force on an object and the special case of balanced forces when the resultant force is zero

1.

What is meant by the resultant force acting on an object?

The single force with the same effect as all the forces acting together.

2.

What happens when the resultant force on an object is zero?

It is in equilibrium and remains stationary or continues at constant velocity.

3.

What are balanced forces?

Forces that combine to give a resultant force of zero.

4.

An object has forces of 15 N to the right and 9 N to the left. What is the resultant force?

15 − 9 = 6 N to the right.

5.

An object has a 20 N upward force and a 20 N downward force. What is the resultant force?

0 N.

6.

How can a resultant force change the motion of an object?

By causing it to accelerate, decelerate or change direction.

9.6P Describe situations where forces can cause rotation

1.

How can a force cause an object to rotate?

When it acts at a distance from a pivot or axis of rotation.

2.

What determines how effective a force is at causing rotation?

The size of the force and its perpendicular distance from the pivot.

3.

Why can pushing a door near its handle produce more rotation than pushing it near its hinges?

The force acts further from the hinges, giving a greater moment.

4.

Give an example of a force causing an object to rotate.

Pushing a spanner around a bolt.

5.

What happens when a force acts at a greater perpendicular distance from a pivot?

It produces a greater turning effect.

6.

Why does the position of the pivot affect the rotational effect of a force?

It changes the perpendicular distance between the force and the pivot.

9.7P Recall and use the equation: moment of a force (newton metre, N m) = force (newton, N) × distance normal to the direction of the force (metre, m)

1.

What equation is used to calculate the moment of a force?

Moment = force × perpendicular distance from the pivot.

2.

What is the unit of moment?

The newton metre (N m).

3.

What does the perpendicular distance in the moment equation represent?

The shortest distance from the pivot to the line of action of the force.

4.

A force of 20 N acts at a perpendicular distance of 0.5 m from a pivot. Calculate the moment.

20 × 0.5 = 10 N m.

5.

A force produces a moment of 60 N m at a perpendicular distance of 0.3 m. Calculate the force.

60 ÷ 0.3 = 200 N.

6.

A force of 15 N produces a moment of 45 N m. Calculate its perpendicular distance from the pivot.

45 ÷ 15 = 3 m.

9.8P Recall and use the principle of moments in situations where rotational forces are in equilibrium: the sum of clockwise moments = the sum of anti-clockwise moments for rotational forces in equilibrium

1.

What is the principle of moments for an object in rotational equilibrium?

The sum of clockwise moments equals the sum of anti-clockwise moments.

2.

What is the relationship between the total clockwise and anti-clockwise moments in equilibrium?

They are equal.

3.

A 10 N force acts 2 m from a pivot. What anti-clockwise moment is needed for rotational equilibrium?

10 × 2 = 20 N m.

4.

A 30 N force acts 0.4 m from a pivot. A second force acts 0.6 m from the pivot on the opposite side. Calculate the second force needed for equilibrium.

(30 × 0.4) ÷ 0.6 = 20 N.

5.

A force of 20 N produces a clockwise moment of 80 N m. What distance from the pivot does it act?

80 ÷ 20 = 4 m.

6.

Why does an object remain rotationally stationary when clockwise and anti-clockwise moments are equal?

The moments cancel, giving a resultant moment of zero.

9.9P Explain how levers and gears transmit the rotational effects of forces

1.

What is a lever?

A rigid object that rotates about a pivot when a force is applied.

2.

How does a lever transmit the rotational effect of a force?

It transmits the turning effect from one point to another around a pivot.

3.

What is the purpose of gears in a mechanical system?

To transmit rotational motion and change speed, direction or turning effect.

4.

How can changing the sizes of gears affect rotational speed?

A larger driven gear rotates more slowly than a smaller driven gear.

5.

How can gears change the turning effect or torque transmitted by a system?

By changing the gear sizes.

6.

Why can a longer lever make it easier to turn or lift an object?

It gives a greater perpendicular distance from the pivot, producing a greater moment for the same force.

9.10 Explain ways of reducing unwanted energy transfer through lubrication

1.

Why does friction cause unwanted energy transfer?

It transfers useful mechanical energy to thermal energy.

2.

How does lubrication reduce friction between moving surfaces?

It forms a layer between the surfaces, reducing direct contact.

3.

What form does much of the unwanted energy become when friction occurs?

Thermal energy in the surfaces and surroundings.

4.

Why can lubrication increase the efficiency of a mechanical system?

Less energy is dissipated through friction.

5.

How does reducing friction affect the amount of thermal energy transferred to the surroundings?

It decreases it.

6.

Give an example of a mechanical system where lubrication can reduce unwanted energy transfer.

Lubricating the moving parts of an engine.

10.1 Describe the structure of the atom, limited to the position, mass and charge of protons, neutrons and electrons

1.

Where are protons, neutrons and electrons located within an atom?

Protons and neutrons are in the nucleus; electrons are outside the nucleus in electron shells.

2.

What is the relative charge of a proton?

+1.

3.

What is the relative charge of a neutron?

0.

4.

What is the relative charge of an electron?

−1.

5.

Which two particles have approximately equal masses?

Protons and neutrons.

6.

Which particle has a much smaller mass than a proton or neutron?

The electron.

10.2 Draw and use electric circuit diagrams representing them with the conventions of positive and negative terminals, and the symbols that represent cells, including batteries, switches, voltmeters, ammeters, resistors, variable resistors, lamps, motors, diodes, thermistors, LDRs and LEDs

1.

What circuit symbol represents a cell?

Two parallel lines, one longer (positive) than the other (negative).

2.

How is a battery represented in a circuit diagram?

Two or more cells connected together.

3.

What circuit symbol represents an ammeter?

A circle containing A.

4.

What circuit symbol represents a voltmeter?

A circle containing V.

5.

Which circuit symbols represent a variable resistor, thermistor and LDR?

A resistor with a diagonal arrow (variable resistor), a resistor with a diagonal line (thermistor), a resistor with arrows pointing towards it (LDR).

6.

Which circuit symbols represent a diode, LED, lamp and motor?

A diode symbol with a line; an LED is a diode symbol with outward arrows; a lamp is a circle with a cross; a motor is a circle containing M.

10.3 Describe the differences between series and parallel circuits

1.

What is a series circuit?

Components connected in a single loop, so there is only one path for current.

2.

What is a parallel circuit?

Components connected in separate branches, providing more than one path for current.

3.

How does the path taken by current differ between series and parallel circuits?

In series there is only one path; in parallel current can split between branches.

4.

What happens to the current at a junction in a parallel circuit?

The total current entering equals the total current leaving.

5.

What happens to other components in a series circuit if one component breaks?

The circuit is broken and current stops everywhere.

6.

Why can components in a parallel circuit operate independently?

Each branch provides a separate path for current.

10.4 Recall that a voltmeter is connected in parallel with a component to measure the potential difference (voltage), in volt, across it

1.

How is a voltmeter connected to a component?

In parallel with the component.

2.

What quantity does a voltmeter measure?

Potential difference.

3.

What is the unit of potential difference?

The volt (V).

4.

Why must a voltmeter be connected in parallel?

So it measures the potential difference across the component.

5.

Where should a voltmeter be connected to measure the potential difference across a resistor?

Across the two terminals of the resistor.

6.

What would happen to the measurement if a voltmeter were incorrectly connected in series?

It would greatly reduce the current, giving an incorrect measurement.

10.5 Explain that potential difference (voltage) is the energy transferred per unit charge passed and hence that the volt is a joule per coulomb

1.

What does potential difference measure?

The energy transferred per unit charge.

2.

How is potential difference related to energy transferred and charge?

V = E ÷ Q.

3.

What does a potential difference of 1 V mean?

1 J of energy is transferred for every 1 C of charge.

4.

What is the relationship between volts, joules and coulombs?

1 V = 1 J/C.

5.

A charge of 5 C transfers 20 J of energy. What is the potential difference?

V = 20 ÷ 5 = 4 V.

6.

A potential difference of 12 V transfers 60 J of energy. How much charge passes?

Q = 60 ÷ 12 = 5 C.

10.6 Recall and use the equation: energy transferred (joule, J) = charge moved (coulomb, C) × potential difference (volt, V) E = Q × V

1.

What equation links energy transferred, charge and potential difference?

E = Q × V.

2.

Calculate the energy transferred when 4 C passes through a potential difference of 12 V.

E = 4 × 12 = 48 J.

3.

A charge of 10 C transfers 240 J of energy. Calculate the potential difference.

V = 240 ÷ 10 = 24 V.

4.

A 9 V battery transfers 180 J of energy. Calculate the charge moved.

Q = 180 ÷ 9 = 20 C.

5.

A charge of 2.5 C passes through a 6 V potential difference. Calculate the energy transferred.

E = 2.5 × 6 = 15 J.

6.

A device transfers 1,200 J when 100 C of charge passes through it. Calculate the potential difference.

V = 1200 ÷ 100 = 12 V.

10.7 Recall that an ammeter is connected in series with a component to measure the current, in amp, in the component

1.

How is an ammeter connected to a component?

In series with the component.

2.

What quantity does an ammeter measure?

Current.

3.

What is the unit of current?

The ampere (A).

4.

Why must an ammeter be connected in series?

So the same current flowing through the component flows through the ammeter.

5.

Where should an ammeter be placed to measure the current through a lamp?

Anywhere in series with the lamp.

6.

What would happen to the circuit if an ammeter were incorrectly connected in parallel?

It would provide a very low-resistance path and could cause a very large, potentially damaging current.

10.8 Explain that an electric current as the rate of flow of charge and the current in metals is a flow of electrons

1.

What is meant by electric current?

The rate of flow of electric charge.

2.

What does the rate of flow of charge describe?

How much charge passes a point per unit time.

3.

Which particles carry electric charge through metals?

Electrons.

4.

In which direction do electrons move through a metal circuit?

From the negative terminal towards the positive terminal.

5.

What happens to current when the same amount of charge passes a point in less time?

The current increases.

6.

How is current different from the amount of charge flowing through a circuit?

Current is the rate at which charge flows, whereas charge is the amount transferred.

10.9 Recall and use the equation: charge (coulomb, C) = current (ampere, A) × time (second, s) Q = I × t

1.

What equation links charge, current and time?

Q = I × t.

2.

Calculate the charge passing through a circuit when a current of 3 A flows for 20 s.

Q = 3 × 20 = 60 C.

3.

A current of 0.5 A flows for 60 s. Calculate the charge transferred.

Q = 0.5 × 60 = 30 C.

4.

A charge of 240 C passes in 30 s. Calculate the current.

I = 240 ÷ 30 = 8 A.

5.

A current of 2 A transfers 500 C of charge. Calculate the time taken.

t = 500 ÷ 2 = 250 s.

6.

How much charge passes through a 12 A circuit in 5 s?

Q = 12 × 5 = 60 C.

10.10 Describe that when a closed circuit includes a source of potential difference there will be a current in the circuit

1.

What is required for current to flow continuously in a circuit?

A complete closed circuit and a source of potential difference.

2.

Why must a circuit be closed for current to flow?

It provides a complete path for charge to flow around.

3.

What role does a cell or battery play in a circuit?

It provides the potential difference that drives charge around the circuit.

4.

What happens to the current when a switch is opened?

The circuit is broken and the current stops.

5.

What happens when a closed circuit contains a source of potential difference?

A current flows through the circuit.

6.

Why does a broken wire prevent current from flowing?

It creates a gap in the circuit, so there is no complete path for charge.

10.11 Recall that current is conserved at a junction in a circuit

1.

What happens to the total current at a junction?

The total current entering equals the total current leaving.

2.

What does conservation of current mean in a parallel circuit?

The current entering equals the sum of the currents in the branches.

3.

A junction has 5 A entering and 2 A leaving through one branch. What current leaves through the other branch?

5 − 2 = 3 A.

4.

A current of 6 A enters a junction and splits into 2 A and another current. What is the other current?

6 − 2 = 4 A.

5.

Why is the total current entering a junction equal to the total current leaving it?

Charge cannot be created or destroyed at the junction.

6.

How can conservation of current be used to calculate an unknown branch current?

Add known branch currents and set their total equal to the current entering, then rearrange.

10.12 Explain how changing the resistance in a circuit changes the current and how this can be achieved using a variable resistor

1.

What happens to current when resistance increases while potential difference remains constant?

It decreases.

2.

What happens to current when resistance decreases while potential difference remains constant?

It increases.

3.

How can a variable resistor change the resistance of a circuit?

By changing the length of resistive material the current flows through.

4.

Why can a variable resistor be used to control current?

Changing the resistance changes the current for a fixed potential difference.

5.

A fixed potential difference is applied to a circuit and its resistance is doubled. What happens to the current?

It is halved.

6.

How could a variable resistor be used to investigate the relationship between resistance and current?

Vary its resistance and measure current for a fixed potential difference.

10.13 Recall and use the equation: potential difference (volt, V) = current (ampere, A) × resistance (ohm, Ω) V = I × R

1.

What equation links potential difference, current and resistance?

V = I × R.

2.

Calculate the potential difference across a 6 Ω resistor carrying 2 A.

V = 2 × 6 = 12 V.

3.

A resistor has a potential difference of 12 V and a current of 3 A. Calculate its resistance.

R = 12 ÷ 3 = 4 Ω.

4.

A 20 Ω resistor has a potential difference of 100 V across it. Calculate the current.

I = 100 ÷ 20 = 5 A.

5.

A current of 0.5 A flows through a 16 Ω resistor. Calculate the potential difference.

V = 0.5 × 16 = 8 V.

6.

What happens to current if resistance increases while potential difference remains constant?

It decreases.

10.14 Explain why, if two resistors are in series, the net resistance is increased, whereas with two in parallel the net resistance is decreased

1.

Why does adding a resistor in series increase the total resistance?

The current has to pass through both resistors.

2.

What happens to the total resistance when resistors are connected in parallel?

It decreases.

3.

Why does a parallel arrangement provide additional paths for current?

It makes it easier for charge to flow through the circuit.

4.

Two 5 Ω resistors are connected in series. What is their total resistance?

5 + 5 = 10 Ω.

5.

Two 10 Ω resistors are connected in parallel. Is their total resistance greater than, equal to, or less than 10 Ω?

Less than 10 Ω.

6.

Why is the total resistance of two parallel resistors less than the resistance of either individual resistor?

The current has more than one path, reducing overall opposition to flow.

10.15 Calculate the currents, potential differences and resistances in series circuits

1.

What happens to the current at every point in a series circuit?

It is the same.

2.

How is the total potential difference shared between components in series?

The potential differences across components add to the supply potential difference.

3.

Two resistors of 4 Ω and 6 Ω are connected in series across a 20 V supply. Calculate the total resistance.

4 + 6 = 10 Ω.

4.

A 12 V supply is connected to two series resistors of 2 Ω and 4 Ω. Calculate the current in the circuit.

R = 6 Ω; I = 12 ÷ 6 = 2 A.

5.

A 10 V supply provides a current of 2 A through a series circuit containing a 3 Ω resistor and an unknown resistor. Calculate the resistance of the unknown resistor.

R_total = 10 ÷ 2 = 5 Ω; unknown = 5 − 3 = 2 Ω.

6.

A series circuit has a current of 0.5 A and a total resistance of 20 Ω. Calculate the supply potential difference.

V = 0.5 × 20 = 10 V.

10.16 Explain the design and construction of series circuits for testing and measuring

1.

Why are components connected in series when measuring the current through them?

The same current flows through every component in a series circuit.

2.

Where should an ammeter be placed in a series circuit?

In series with the component being tested.

3.

How should a voltmeter be connected when measuring the potential difference across a component?

In parallel across the component.

4.

Why should the circuit include a switch when carrying out electrical measurements?

To disconnect the circuit when not taking measurements, preventing unnecessary heating.

5.

Why can a variable resistor be useful in a testing circuit?

It allows the current and potential difference to be varied safely.

6.

What measurements are needed to determine the resistance of a component using R = V ÷ I?

The potential difference across it and the current through it.

10.17 Core Practical: Construct electrical circuits to: a investigate the relationship between potential difference, current and resistance for a resistor and a filament lamp b test series and parallel circuits using resistors and filament lamps

1.

How can a circuit be constructed to investigate the relationship between potential difference and current?

Connect the component with an ammeter in series and a voltmeter in parallel; vary the potential difference and record current.

2.

How should an ammeter and voltmeter be connected when investigating a component?

Ammeter in series, voltmeter in parallel.

3.

How can the resistance of a resistor be calculated from experimental measurements?

R = V ÷ I.

4.

How can the behaviour of a filament lamp be compared with that of a fixed resistor?

A fixed resistor has approximately constant resistance; a filament lamp's resistance increases as it heats up.

5.

What should be measured when comparing series and parallel circuits containing lamps and resistors?

The current and potential difference in each circuit.

6.

Why should repeated measurements be taken during an electrical investigation?

To improve reliability and identify anomalous results.

10.18 Explain how current varies with potential difference for the following devices and how this relates to resistance: a filament lamps b diodes c fixed resistors

1.

How does current vary with potential difference for a fixed resistor at constant temperature?

Current is directly proportional to potential difference.

2.

Why does the resistance of a filament lamp increase as its potential difference increases?

The filament gets hotter, increasing its resistance.

3.

How does heating affect the resistance of a filament lamp?

Heating increases the resistance of the filament.

4.

How does current behave through a diode when it is forward biased?

Very little current flows below a threshold potential difference, then current increases rapidly.

5.

Why does a diode have a very high resistance when reverse biased?

Almost no current flows.

6.

How can a current-potential difference graph be used to determine whether a component has constant resistance?

A straight line through the origin indicates constant resistance; a changing gradient indicates changing resistance.

10.19 Describe how the resistance of a light-dependent resistor (LDR) varies with light intensity

1.

What happens to the resistance of an LDR when light intensity increases?

It decreases.

2.

What happens to the resistance of an LDR when light intensity decreases?

It increases.

3.

Why can an LDR be used as a light sensor?

Its resistance changes with light intensity.

4.

How could an LDR be used to switch a circuit on when it becomes dark?

Its increased resistance in darkness changes the potential difference or current in a control circuit.

5.

What happens to the current through an LDR if its resistance decreases while potential difference remains constant?

It increases.

6.

How does light intensity affect the resistance of an LDR?

Increasing light intensity decreases the resistance.

10.20 Describe how the resistance of a thermistor varies with change of temperature (negative temperature coefficient thermistors only)

1.

What happens to the resistance of an NTC thermistor when temperature increases?

It decreases.

2.

What happens to the resistance of an NTC thermistor when temperature decreases?

It increases.

3.

What does NTC mean for a thermistor?

Negative temperature coefficient.

4.

Why can an NTC thermistor be used as a temperature sensor?

Its resistance changes with temperature.

5.

What happens to current through an NTC thermistor when its temperature increases at constant potential difference?

It increases, because resistance decreases.

6.

How could an NTC thermistor be used in a temperature-sensitive circuit?

A change in temperature changes the current or potential difference.

10.21 Explain how the design and use of circuits can be used to explore the variation of resistance in the following devices: a filament lamps b diodes c thermistors d LDRs

1.

How can potential difference and current measurements be used to investigate resistance?

Measure V and I, then calculate R = V ÷ I.

2.

How can a variable resistor help investigate the resistance of a filament lamp?

It allows the current to be varied while V and I are measured.

3.

How can the forward and reverse behaviour of a diode be investigated?

Measure current for different potential differences connected in the forward and reverse directions.

4.

How can a thermistor circuit be used to investigate the effect of temperature on resistance?

Vary the temperature and measure V and I at each temperature.

5.

How can an LDR circuit be used to investigate the effect of light intensity on resistance?

Vary the light intensity and measure V and I at each intensity.

6.

Why can a graph of potential difference against current help investigate how resistance varies?

A changing gradient shows that resistance varies.

10.22 Recall that, when there is an electric current in a resistor, there is an energy transfer which heats the resistor

1.

What happens to energy when an electric current flows through a resistor?

Electrical energy is transferred to the thermal energy store of the resistor.

2.

Which energy store increases when a resistor heats up?

Its thermal energy store.

3.

Why does a resistor become hot when current flows through it?

Electrical energy is transferred to thermal energy as current flows through the resistance.

4.

What happens to the temperature of a resistor when electrical energy is transferred to its thermal energy store?

It increases.

5.

What type of energy transfer occurs in an electrical resistor?

Electrical energy transferred to thermal energy.

6.

Give one example of a useful resistor heating effect.

An electric heater.

10.23 Explain that electrical energy is dissipated as thermal energy in the surroundings when an electrical current does work against electrical resistance

1.

What happens to electrical energy when current encounters resistance?

It is transferred to thermal energy.

2.

What does it mean for electrical energy to be dissipated?

It is transferred to the surroundings, usually as thermal energy, and is no longer usefully available.

3.

Why is thermal energy transferred to the surroundings by a resistor?

The resistor becomes heated by the electrical current.

4.

Why is energy dissipated in the wires and components of a circuit?

Resistance causes electrical energy to be transferred to thermal energy in them.

5.

How does electrical resistance cause a transfer of energy to the thermal energy store?

Electrons collide with particles in the material, transferring energy.

6.

Why can unwanted resistance reduce the efficiency of an electrical system?

It causes useful electrical energy to be transferred as heat.

10.24 Explain the energy transfer (in 10.22 above) as the result of collisions between electrons and the ions in the lattice

1.

What particles move through a metal when an electric current flows?

Electrons.

2.

What particles form the lattice in a metal?

Positive ions.

3.

What happens when electrons collide with ions in the metal lattice?

Energy is transferred to the ions.

4.

How do electron-ion collisions cause a resistor to heat up?

The collisions increase the vibrations of the ions, increasing thermal energy.

5.

How is electrical energy transferred to the thermal energy store during these collisions?

Through collisions between electrons and ions.

6.

Why does increased resistance result in greater energy dissipation as heating?

Greater resistance causes more energy to be dissipated as thermal energy for a given current.

10.25 Explain ways of reducing unwanted energy transfer through low resistance wires

1.

Why does electrical resistance cause unwanted energy transfer as heating?

It transfers electrical energy to thermal energy.

2.

How can using low-resistance wires reduce unwanted energy transfer?

They reduce the amount of electrical energy dissipated as heat.

3.

Why are thick wires generally useful for reducing resistance?

They have a larger cross-sectional area.

4.

Why are low-resistance wires useful for transmitting electrical energy?

They reduce energy losses over long distances.

5.

How does reducing resistance affect the amount of electrical energy dissipated as thermal energy?

It reduces it.

6.

Why are low-resistance materials used in electrical cables?

To minimise unwanted heating and energy loss.

10.26 Describe the advantages and disadvantages of the heating effect of an electric current

1.

What is one useful application of the heating effect of an electric current?

An electric heater.

2.

Why is the heating effect useful in an electric kettle?

It transfers electrical energy to thermal energy, heating the water.

3.

Why is the heating effect useful in an electric heater?

Resistance transfers electrical energy to thermal energy, heating the surroundings.

4.

Why can heating caused by resistance be an unwanted energy transfer?

It transfers energy away from the intended useful output.

5.

How can unwanted heating affect electrical cables?

It can cause them to become hot and waste electrical energy.

6.

What is the main advantage and disadvantage of the heating effect of electric current?

Advantage: useful heating; disadvantage: unwanted resistance causes energy loss and heating.

10.27 Use the equation: energy transferred (joule, J) = current (ampere, A) × potential difference (volt, V) × time (second, s) E = I × V × t

1.

What equation links energy transferred, current, potential difference and time?

E = I × V × t.

2.

A current of 2 A flows through a 12 V device for 30 s. Calculate the energy transferred.

E = 2 × 12 × 30 = 720 J.

3.

A 5 A current flows through a 20 V device for 10 s. Calculate the energy transferred.

E = 5 × 20 × 10 = 1,000 J.

4.

A device transfers 6,000 J using a current of 5 A at 20 V. Calculate the operating time.

t = 6000 ÷ (5 × 20) = 60 s.

5.

A device transfers 2,400 J in 60 s at a potential difference of 12 V. Calculate the current.

I = 2400 ÷ (12 × 60) = 3.33 A.

6.

A current of 0.5 A flows for 120 s through a 10 V device. Calculate the energy transferred.

E = 0.5 × 10 × 120 = 600 J.

10.28 Describe power as the energy transferred per second and recall that it is measured in watt

1.

What is power?

The rate of energy transfer.

2.

What does a high power rating indicate about the rate of energy transfer?

It transfers energy at a faster rate.

3.

What is the unit of power?

The watt (W).

4.

What does a power rating of 1 W mean?

1 J of energy is transferred every second.

5.

How much energy does a 500 W device transfer each second?

500 J.

6.

Which transfers energy faster: a 100 W device or a 1,000 W device?

The 1,000 W device.

10.29 Recall and use the equation: power (watt, W) = energy transferred (joule, J) ÷ time taken (second, s) P = E ÷ t

1.

What equation is used to calculate electrical power from energy and time?

P = E ÷ t.

2.

A device transfers 4,000 J in 20 s. Calculate its power.

P = 4000 ÷ 20 = 200 W.

3.

A 600 W appliance operates for 30 s. Calculate the energy transferred.

E = 600 × 30 = 18,000 J.

4.

A device transfers 9,000 J at a power of 300 W. Calculate the time taken.

t = 9000 ÷ 300 = 30 s.

5.

A heater transfers 12,000 J in 60 s. Calculate its power.

P = 12,000 ÷ 60 = 200 W.

6.

A motor has a power of 250 W and operates for 2 minutes. Calculate the energy transferred.

t = 120 s; E = 250 × 120 = 30,000 J.

10.30 Explain how the power transfer in any circuit device is related to the potential difference across it and the current in it

1.

How is the power transferred by a circuit device related to potential difference?

Power increases when potential difference increases, for constant current.

2.

How is the power transferred by a circuit device related to current?

Power increases when current increases, for constant potential difference.

3.

What happens to power if the potential difference across a device increases while current remains constant?

Power increases.

4.

What happens to power if current increases while potential difference remains constant?

Power increases.

5.

A device operates at 12 V and 2 A. What is its power?

P = 2 × 12 = 24 W.

6.

Why does a device with both a greater potential difference and greater current transfer energy more rapidly?

Power is the rate of energy transfer, and both factors increase this rate.

10.31 Recall and use the equations: electrical power (watt, W) = current (ampere, A) × potential difference (volt, V) P = I × V; electrical power (watt, W) = current squared (ampere², A²) × resistance (ohm, Ω) P = I² × R

1.

What equation calculates electrical power using current and potential difference?

P = I × V.

2.

What equation calculates electrical power using current and resistance?

P = I² × R.

3.

A device draws 4 A from a 12 V supply. Calculate its power using P = I × V.

P = 4 × 12 = 48 W.

4.

A 5 Ω resistor carries a current of 3 A. Calculate its power using P = I² × R.

P = 3² × 5 = 45 W.

5.

A device has a power of 1,000 W and operates at 250 V. Calculate its current.

I = 1000 ÷ 250 = 4 A.

6.

A resistor dissipates 200 W while carrying a current of 5 A. Calculate its resistance.

R = 200 ÷ 5² = 8 Ω.

10.32 Describe how, in different domestic devices, energy is transferred from batteries and the a.c. mains to the energy of motors and heating devices

1.

What type of energy is transferred by a battery to an electrical device?

Chemical energy transferred to electrical energy.

2.

How does an electric motor transfer electrical energy?

To kinetic energy, causing movement.

3.

How does an electric heater transfer electrical energy?

To thermal energy.

4.

Give one domestic device that uses a motor to transfer energy.

A washing machine.

5.

Give one domestic device that uses electrical heating.

An electric kettle.

6.

How can the same electrical supply produce different useful energy transfers in different domestic devices?

Different devices contain different components that convert electrical energy into different useful forms.

10.33 Explain the difference between direct and alternating voltage

1.

What is direct voltage?

A voltage with constant polarity, driving charge in one direction.

2.

What is alternating voltage?

A voltage that repeatedly changes polarity and direction with time.

3.

How does direct voltage differ from alternating voltage in terms of direction?

Direct voltage has a constant direction; alternating voltage periodically reverses.

4.

What type of voltage is supplied by a cell?

Direct voltage.

5.

What type of voltage is supplied by the UK mains?

Alternating voltage.

6.

How does the direction of an alternating voltage change with time?

It repeatedly reverses.

10.34 Describe direct current (d.c.) as movement of charge in one direction only and recall that cells and batteries supply direct current (d.c.)

1.

What is direct current?

The movement of charge in one direction only.

2.

In what direction does charge move in a d.c. circuit?

In one direction only.

3.

What devices supply direct current?

Cells and batteries.

4.

Do cells produce d.c. or a.c.?

d.c.

5.

Do batteries produce d.c. or a.c.?

d.c.

6.

How does the direction of charge movement in d.c. differ from a.c.?

In d.c. charge moves in one direction only; in a.c. the direction repeatedly changes.

10.35 Describe that in alternating current (a.c.) the movement of charge changes direction

1.

What is alternating current?

Current in which the direction of charge movement changes repeatedly.

2.

What happens to the direction of charge movement in an a.c. circuit?

It repeatedly reverses.

3.

How does a.c. differ from d.c.?

a.c. changes direction periodically; d.c. flows in one direction only.

4.

Does charge in an a.c. circuit continually move in one direction?

No.

5.

Why is mains electricity described as alternating current?

The direction of charge movement changes repeatedly.

6.

What happens to the direction of current during one complete a.c. cycle?

It changes direction and then returns to its original direction.

10.36 Recall that in the UK the domestic supply is a.c., at a frequency of 50 Hz and a voltage of about 230 V

1.

What type of current is supplied to UK homes?

Alternating current (a.c.).

2.

What is the frequency of the UK domestic a.c. supply?

50 Hz.

3.

What is the approximate voltage of the UK domestic supply?

230 V.

4.

What does a frequency of 50 Hz mean for the UK mains supply?

50 complete cycles occur each second.

5.

Is the UK domestic supply approximately 230 V d.c. or a.c.?

a.c.

6.

How many complete cycles occur each second in the UK mains supply?

50.

10.37 Explain the difference in function between the live and the neutral mains input wires

1.

What is the function of the live wire?

It carries the alternating potential difference to the appliance.

2.

What is the function of the neutral wire?

It provides the return path for current.

3.

Which mains wire carries the alternating potential difference to a domestic appliance?

The live wire.

4.

Which mains wire provides the return path for current?

The neutral wire.

5.

Why is the live wire dangerous even when the neutral wire is at approximately zero potential relative to Earth?

It is at a large potential difference relative to Earth, so touching it can cause a dangerous current.

6.

Why must the live and neutral wires have different functions in a domestic circuit?

The live supplies potential difference and the neutral completes the circuit.

10.38 Explain the function of an earth wire and of fuses or circuit breakers in ensuring safety

1.

What is the function of the earth wire in a domestic appliance?

It provides a low-resistance path to Earth if a fault makes a metal case live.

2.

Why is the earth wire important for appliances with metal cases?

It allows a large current to flow if the case becomes live, helping protective devices disconnect the supply.

3.

What does a fuse do when the current becomes too large?

It melts, breaking the circuit.

4.

How does a circuit breaker protect a circuit?

It automatically switches off the circuit when the current becomes too large.

5.

Why can a fuse or circuit breaker prevent overheating of wires?

They stop excessive current from continuing to flow.

6.

How do the earth wire and fuse or circuit breaker work together to improve electrical safety?

The earth wire provides a path for a large fault current, causing the fuse to melt or breaker to trip.

10.39 Explain why switches and fuses should be connected in the live wire of a domestic circuit

1.

Why should a switch be connected in the live wire?

It disconnects the dangerous potential difference when switched off.

2.

Why should a fuse be connected in the live wire?

It disconnects the appliance from the supply if the current becomes too large.

3.

What could happen if a switch were connected only in the neutral wire?

The appliance could remain connected to the live potential difference even when switched off.

4.

Why does disconnecting the live wire make an appliance safer when switched off?

It removes the dangerous potential difference from the appliance.

5.

How does a fuse in the live wire protect an appliance?

If excessive current flows, it melts and disconnects the appliance from the live supply.

6.

Why would placing a fuse only in the neutral wire be unsafe?

The appliance could remain connected to the live wire at a dangerous potential difference even after the fuse has blown.

10.40 Recall the potential differences between the live, neutral and earth mains wires

1.

What is the potential difference between the live and neutral wires in the UK mains supply?

About 230 V.

2.

What is the potential difference between the live and earth wires?

About 230 V.

3.

What is the potential difference between the neutral and earth wires under normal conditions?

Approximately 0 V.

4.

Which mains wire is at approximately 230 V relative to earth?

The live wire.

5.

Which mains wires are approximately at the same potential under normal conditions?

Neutral and earth.

6.

Why is the live wire dangerous relative to the neutral and earth wires?

It is at a large potential difference relative to them.

10.41 Explain the dangers of providing any connection between the live wire and earth

1.

Why is a connection between the live wire and earth dangerous?

It can cause a large current to flow because of the large potential difference.

2.

What can happen if a person provides a path between live and earth?

They can receive an electric shock, potentially causing serious injury or death.

3.

Why can current flow through a person connected between live and earth?

The body can provide a conducting path.

4.

How can an earth connection cause a large current to flow?

The large potential difference between live and Earth can drive a large current through a low-resistance path.

5.

How can a fuse or circuit breaker respond to a live-to-earth fault?

The large fault current can cause a fuse to melt or a circuit breaker to trip.

6.

Why should people never make direct connections between live wires and earth?

Direct connections can cause large currents, electric shocks, overheating and fires.

10.42 Describe, with examples, the relationship between the power ratings for domestic electrical appliances and the changes in stored energy when they are in use

1.

What does the power rating of a domestic appliance indicate?

The rate at which it transfers energy.

2.

What happens to the rate of energy transfer when an appliance has a higher power rating?

It increases.

3.

Which transfers energy faster: a 2,000 W kettle or a 1,000 W kettle?

The 2,000 W kettle.

4.

A 1,500 W heater operates for 60 s. How much energy does it transfer?

E = 1500 × 60 = 90,000 J.

5.

A 100 W lamp operates for 5 minutes. Calculate the energy transferred.

t = 300 s; E = 100 × 300 = 30,000 J.

6.

Why does a high-power appliance transfer more energy in the same amount of time than a low-power appliance?

Power is the rate of energy transfer, so higher power means more energy transferred per second.

11.1P Explain how an insulator can be charged by friction, through the transfer of electrons

1.

How can an insulator become electrically charged by friction?

Rubbing it against another material can transfer electrons between the two materials.

2.

Which particles are transferred when an insulator is charged by friction?

Electrons.

3.

Why can electrons be transferred between two different insulating materials?

They can move between the materials when rubbed together.

4.

What happens when two insulating materials are rubbed together?

Electrons are transferred from one material to the other, leaving the materials oppositely charged.

5.

Why does rubbing an insulator not cause protons to transfer between the materials?

Protons are held tightly in the nuclei of atoms and cannot move between materials.

6.

How does friction result in one insulator gaining electrons and the other losing electrons?

Friction causes electrons to transfer from one insulator to the other.

11.2P Explain how the material gaining electrons becomes negatively charged and the material losing electrons is left with an equal positive charge

1.

What charge does a material gain when it gains electrons?

Negative.

2.

What charge does a material have when it loses electrons?

Positive.

3.

Why does gaining electrons make an object negatively charged?

Electrons have a negative charge.

4.

Why does losing electrons make an object positively charged?

It leaves an excess of positive charge.

5.

Why are the positive and negative charges equal in magnitude when electrons are transferred between two initially neutral materials?

The amount of negative charge gained equals the amount lost by the other material.

6.

A neutral insulator gains 5 electrons while another loses the same 5 electrons. What charge does each material acquire?

One becomes negatively charged, the other equally positively charged.

11.3P Recall that like charges repel and unlike charges attract

1.

What happens when two positively charged objects are brought together?

They repel.

2.

What happens when two negatively charged objects are brought together?

They repel.

3.

What happens when a positive and negative charge are brought together?

They attract.

4.

What is meant by like charges?

Charges of the same type.

5.

What is meant by unlike charges?

Charges of different types.

6.

How can the force between two charged objects be used to identify whether their charges are like or unlike?

Repulsion indicates like charges; attraction indicates unlike charges.

11.4P Explain common electrostatic phenomena in terms of movement of electrons, including a shocks from everyday objects b lightning c attraction by induction such as a charged balloon attracted to a wall and a charged comb picking up small pieces of paper

1.

How can an electrostatic shock occur when a person touches a charged object?

Electrons suddenly transfer between the charged object and the person, producing a brief current.

2.

How does the movement of electrons contribute to the formation of lightning?

Electrons move between regions of charge in clouds or between a cloud and the ground.

3.

Why can a charged balloon be attracted to a neutral wall?

It causes electrons in the wall to redistribute, leaving an opposite charge closer to the balloon.

4.

What is meant by electrostatic induction?

The redistribution of electrons within a neutral object caused by a nearby charged object.

5.

Why can a charged comb attract small pieces of paper?

It induces a separation of charge in the paper, producing attraction.

6.

How does the redistribution of electrons explain the attraction between a charged object and a neutral object?

The charged object causes electrons in the neutral object to redistribute, producing attraction.

11.5P Explain how earthing removes excess charge by movement of electrons

1.

What is meant by earthing an electrically charged object?

Providing a conducting path between the object and the Earth.

2.

How does earthing remove excess negative charge?

Excess electrons flow from the object to the Earth.

3.

How does earthing remove a positive charge from an object?

Electrons flow from the Earth onto the object.

4.

In which direction do electrons move when a negatively charged object is earthed?

From the object to the Earth.

5.

Why can Earth act as a source or sink of electrons?

It is extremely large and can gain or lose electrons without becoming significantly charged.

6.

How does earthing return a charged object towards electrical neutrality?

Excess electrons move to or from Earth until the object becomes neutral.

11.6P Explain some of the uses of electrostatic charges in everyday situations, including insecticide sprayers

1.

How can electrostatic charges be used in an insecticide sprayer?

Insecticide droplets are given an electric charge as they are sprayed.

2.

Why can charged insecticide droplets spread out from one another?

Droplets with the same charge repel each other.

3.

How can electrostatic charging help insecticide reach plant surfaces?

The charged droplets are attracted to the plants and spread over their surfaces.

4.

Why can charged droplets be attracted to oppositely charged or induced charges on plants?

Charged droplets are attracted to opposite or induced charges on plant surfaces.

5.

What advantage does electrostatic charging provide when spraying insecticide?

It gives more even coverage and reduces waste.

6.

How does electrostatic repulsion between similarly charged droplets affect the spray?

It causes them to spread apart, producing a wider and more even spray.

11.7P Describe some of the dangers of sparking in everyday situations, including fuelling cars, and explain the use of earthing to prevent dangerous build-up of charge

1.

Why can electrostatic sparks be dangerous when fuelling a car?

A spark could ignite flammable fuel vapour.

2.

How can a build-up of electrostatic charge produce a spark?

A large potential difference can build up, causing electrons to suddenly move through the air.

3.

Why can sparks be particularly dangerous around flammable fuels?

The spark can ignite the fuel vapour and cause a fire or explosion.

4.

How does earthing help prevent a dangerous build-up of charge?

It provides a path for excess charge to flow safely to Earth.

5.

Why can connecting equipment to Earth reduce the risk of electrostatic sparking?

It allows excess electrons to flow away, reducing the charge build-up.

6.

How does the movement of excess electrons to Earth reduce the danger when handling flammable substances?

Electrons flow to Earth instead of suddenly discharging as a spark near flammable substances.

11.8P Define an electric field as the region where an electric charge experiences a force

1.

What is an electric field?

A region where an electric charge experiences a force.

2.

What happens to a charge placed within an electric field?

It experiences an electric force.

3.

Around what type of object does an electric field exist?

Charged objects.

4.

How can the presence of an electric field be detected?

A test charge can be used, as it experiences a force within the field.

5.

What force does a charged object experience when placed in an electric field?

An electric force.

6.

How is an electric field different from the physical movement of charged particles?

It is a region in which charges experience forces; it does not require particles to move.

11.9P Describe the shape and direction of the electric field around a point charge and between parallel plates and relate the strength of the field to the concentration of lines

1.

What is the shape of the electric field around an isolated positive point charge?

Field lines radiate outwards from the charge.

2.

What is the direction of electric field lines around a positive point charge?

They point away from the charge.

3.

What is the direction of electric field lines around a negative point charge?

They point towards the charge.

4.

What do electric field lines look like between two oppositely charged parallel plates?

Straight, parallel and evenly spaced, directed from the positive plate towards the negative plate.

5.

What does a greater concentration of electric field lines indicate about field strength?

A stronger electric field.

6.

Why is the electric field between parallel plates approximately uniform away from the edges?

The field lines are approximately parallel and evenly spaced there.

11.10P Explain how the concept of an electric field helps to explain the phenomena of static electricity

1.

How does an electric field explain the force between charged objects?

Charged objects produce electric fields, and charges within these fields experience forces.

2.

How can an electric field explain the attraction of a charged balloon to a neutral wall?

The balloon's electric field causes electrons in the wall to redistribute, producing attraction.

3.

How does the electric field around a charged object affect nearby charges?

It exerts a force on them.

4.

How can electric fields explain repulsion between like charges?

Like charges produce forces that push the charges apart.

5.

How can electric fields explain attraction between unlike charges?

Unlike charges produce forces that pull the charges together.

6.

Why is the concept of an electric field useful for explaining static electricity?

It explains the forces acting between charged objects without them needing to touch.

12.1 Recall that unlike magnetic poles attract and like magnetic poles repel

1.

What happens when two north magnetic poles are brought together?

They repel.

2.

What happens when two south magnetic poles are brought together?

They repel.

3.

What happens when a north pole and a south pole are brought together?

They attract.

4.

What is meant by like magnetic poles?

Two poles of the same type.

5.

What is meant by unlike magnetic poles?

A north pole and a south pole.

6.

How can the interaction between two magnetic poles be used to determine whether they are like or unlike?

Attraction indicates unlike poles; repulsion indicates like poles.

12.2 Describe the uses of permanent and temporary magnetic materials including cobalt, steel, iron and nickel

1.

What is a permanent magnetic material?

One that remains magnetised after the external magnetic field is removed.

2.

What is a temporary magnetic material?

One that becomes magnetised in a field but loses most or all of its magnetism when the field is removed.

3.

Why is steel suitable for making permanent magnets?

It is difficult to magnetise but retains its magnetism.

4.

Why is iron suitable for making temporary magnets?

It is easily magnetised and loses its magnetism readily.

5.

What are cobalt and nickel used for in magnetic materials?

Making permanent magnets and magnetic alloys.

6.

What type of magnetic material would be suitable for an electromagnet core, and why?

Iron, because it is easily magnetised and demagnetised.

12.3 Explain the difference between permanent and induced magnets

1.

What is a permanent magnet?

A magnet that remains magnetised when the external field is removed.

2.

What is an induced magnet?

A material that becomes magnetised when placed in an external magnetic field.

3.

How does an induced magnet differ from a permanent magnet?

A permanent magnet retains its magnetism; an induced magnet remains magnetised only while influenced by an external field.

4.

Why does an induced magnet lose its magnetism when the external magnetic field is removed?

The magnetic domains become less aligned when the field is removed.

5.

How can a magnetic material become temporarily magnetised?

By placing it near a magnet, causing its domains to align temporarily.

6.

Why are soft magnetic materials useful for making induced magnets?

They are easily magnetised and demagnetised.

12.4 Describe the shape and direction of the magnetic field around bar magnets and for a uniform field, and relate the strength of the field to the concentration of lines

1.

What is the shape of the magnetic field around a bar magnet?

The field lines form curved loops around the magnet.

2.

What is the direction of magnetic field lines outside a bar magnet?

From north to south.

3.

In which direction do magnetic field lines point between the poles of a bar magnet?

From north to south.

4.

What does a uniform magnetic field look like?

Straight, parallel and evenly spaced field lines.

5.

What does the concentration of magnetic field lines indicate about field strength?

A greater concentration indicates a stronger field.

6.

Where is the magnetic field strongest around a bar magnet?

At the poles.

12.5 Describe the use of plotting compasses to show the shape and direction of the field of a magnet and the Earth's magnetic field

1.

How can plotting compasses be used to investigate a magnetic field?

Place a compass at different positions around the magnet and mark the direction its needle points.

2.

What does the needle of a plotting compass indicate?

The direction of the magnetic field.

3.

How can several compass positions be used to map a magnetic field?

Mark the direction of the needle at each position and join the points to produce field lines.

4.

How can plotting compasses show the direction of a bar magnet's magnetic field?

The compass needle aligns with the field, showing its direction at each position.

5.

How can plotting compasses be used to investigate Earth's magnetic field?

Place a compass at different positions around Earth to determine the field's direction.

6.

Why should the compass be moved to several different positions when plotting a magnetic field?

To map the shape and direction of the whole field.

12.6 Explain how the behaviour of a magnetic compass is related to evidence that the core of the Earth must be magnetic

1.

Why does a compass needle point approximately north-south?

It aligns with Earth's magnetic field.

2.

What does the alignment of a compass needle provide evidence for?

That Earth has a magnetic field.

3.

Why does Earth's magnetic field affect a compass?

It exerts a force on the compass needle.

4.

What does the existence of Earth's magnetic field suggest about its interior?

That it contains magnetic material or produces a magnetic field.

5.

Why does the compass behave as though it is interacting with a large magnet?

It aligns with Earth's magnetic field.

6.

How does compass behaviour provide evidence that Earth's core is magnetic?

The compass aligns with Earth's magnetic field, showing the core must be magnetic.

12.7 Describe how to show that a current can create a magnetic effect around a long straight conductor, describing the shape of the magnetic field produced and relating the direction of the magnetic field to the direction of the current

1.

How can you demonstrate that a current-carrying wire produces a magnetic field?

Pass a current through a straight wire and place plotting compasses around it; the needles change direction.

2.

What is the shape of the magnetic field around a long straight current-carrying conductor?

Concentric circles centred on the conductor.

3.

How does the direction of the magnetic field depend on the direction of current?

Reversing the current reverses the field direction.

4.

What happens to the magnetic field when the current is switched off?

It disappears.

5.

How can plotting compasses be used to investigate the magnetic field around a straight conductor?

Place them at different positions around the wire and observe the needle directions.

6.

What happens to the direction of the magnetic field if the current direction is reversed?

It reverses.

12.8 Recall that the strength of the field depends on the size of the current and the distance from the long straight conductor

1.

What happens to the magnetic field strength around a straight conductor when the current increases?

It becomes stronger.

2.

What happens to magnetic field strength as the distance from a straight conductor increases?

It becomes weaker.

3.

How does doubling the current qualitatively affect the magnetic field strength?

It increases the field strength.

4.

Where is the magnetic field strongest around a current-carrying straight conductor?

Close to the conductor.

5.

Why does the magnetic field become weaker further from the conductor?

The field spreads out with increasing distance.

6.

Which two factors determine the strength of the magnetic field around a long straight conductor?

The size of the current and the distance from the conductor.

12.9 Explain how inside a solenoid (an example of an electromagnet) the fields from individual coils a add together to form a very strong almost uniform field along the centre of the solenoid b cancel to give a weaker field outside the solenoid

1.

What is a solenoid?

A coil of wire consisting of many loops.

2.

What happens to the magnetic fields from individual coils inside a solenoid?

They add together.

3.

Why is the magnetic field along the centre of a solenoid strong?

The fields from the coils reinforce each other.

4.

Why is the magnetic field inside a solenoid approximately uniform?

The field lines are approximately parallel and evenly spaced.

5.

What happens to the magnetic fields from the coils outside a solenoid?

They partially cancel.

6.

Why is the magnetic field outside a solenoid much weaker than the field inside?

The fields add inside but largely cancel outside.

12.10 Recall that a current carrying conductor placed near a magnet experiences a force and that an equal and opposite force acts on the magnet

1.

What happens when a current-carrying conductor is placed in a magnetic field?

It experiences a force.

2.

What causes the force on a current-carrying conductor?

The interaction between the magnetic field of the magnet and the field produced by the conductor.

3.

What happens to the magnet when it exerts a force on the conductor?

It experiences an equal and opposite force.

4.

How are the forces on the conductor and magnet related?

Equal in magnitude, opposite in direction.

5.

What happens to the force on the conductor if the current is switched off?

It disappears.

6.

How does this interaction demonstrate Newton's third law?

The conductor and magnet exert equal and opposite forces on each other.

12.11 Explain that magnetic forces are due to interactions between magnetic fields

1.

What causes a magnetic force between two magnetic objects?

The interaction between their magnetic fields.

2.

How do two interacting magnetic fields produce a force?

The interacting fields produce forces on the objects producing them.

3.

Why does a current-carrying conductor experience a force near a magnet?

The magnetic field around the conductor interacts with the magnetic field of the magnet.

4.

How does the magnetic field around a conductor interact with the magnetic field of a magnet?

The two fields interact, producing a force on the conductor.

5.

Why can changing the direction of one magnetic field change the direction of the force?

Reversing one field changes the interaction between the fields.

6.

How can magnetic field interactions explain attraction and repulsion?

Interacting fields can produce forces that cause objects to attract or repel.

12.12 Recall and use Fleming's left-hand rule to represent the relative directions of the force, the current and the magnetic field for cases where they are mutually perpendicular

1.

What does Fleming's left-hand rule determine?

The relative directions of the force, current and magnetic field.

2.

Which finger represents the direction of the magnetic field in Fleming's left-hand rule?

The first finger.

3.

Which finger represents the direction of current?

The second finger.

4.

Which direction does the thumb represent?

The direction of the force.

5.

When can Fleming's left-hand rule be applied directly?

When force, current and field are mutually perpendicular.

6.

If the direction of the current is reversed while the magnetic field remains unchanged, what happens to the direction of the force?

It reverses.

12.13 Use the equation: force on a conductor at right angles to a magnetic field carrying a current (newton, N) = magnetic flux density (tesla, T or newton per ampere metre, N/A m) × current (ampere, A) × length (metre, m) F = B × I × l

1.

What equation is used to calculate the force on a current-carrying conductor in a magnetic field?

F = B × I × l.

2.

What conditions must apply for F = B × I × l to be used directly?

The conductor must be at right angles to the magnetic field.

3.

A conductor carries a current of 4 A through a magnetic field of 0.5 T. If its length is 0.2 m, calculate the force.

F = 0.5 × 4 × 0.2 = 0.4 N.

4.

A conductor experiences a force of 6 N in a 0.3 T magnetic field while carrying 5 A. Calculate its length.

l = 6 ÷ (0.3 × 5) = 4 m.

5.

A 0.4 m conductor carries 3 A and experiences a force of 2.4 N. Calculate the magnetic flux density.

B = 2.4 ÷ (3 × 0.4) = 2 T.

6.

A 0.5 m conductor in a 0.8 T magnetic field experiences a force of 4 N. Calculate the current.

I = 4 ÷ (0.8 × 0.5) = 10 A.

12.14P Explain how the force on a conductor in a magnetic field is used to cause rotation in electric motor

1.

What causes a current-carrying conductor in a magnetic field to experience a force?

The interaction between the conductor's current and the magnetic field.

2.

How can forces on opposite sides of a current-carrying coil cause rotation?

Forces act in opposite directions, producing a turning effect.

3.

Why do the forces on the two sides of a motor coil act in opposite directions?

The current flows in opposite directions on the two sides.

4.

What happens to the coil when the forces form a turning effect?

It rotates.

5.

What is the function of the split-ring commutator in a simple electric motor?

It reverses the current every half-turn so rotation continues in the same direction.

6.

How does an electric motor use the motor effect to produce continuous rotation?

The magnetic field exerts forces on the current-carrying coil, and the commutator reverses the current every half-turn.

13.1P Explain how to produce an electric current by the relative movement of a magnet and a conductor a on a small scale in the laboratory b in the large-scale generation of electrical energy

1.

How can a current be produced by moving a magnet relative to a conductor?

A potential difference is induced when they move relative to each other; if the circuit is complete, a current flows.

2.

What happens when a magnet is moved through a coil of wire?

A potential difference is induced across the coil, producing a current if the circuit is complete.

3.

How can electromagnetic induction be demonstrated in a laboratory?

Connect a coil to a sensitive ammeter and move a bar magnet into and out of the coil.

4.

Why does relative movement between a magnet and conductor produce a potential difference?

The magnetic field through the conductor changes, inducing a potential difference.

5.

How is electromagnetic induction used to generate electrical energy on a large scale?

Generators rotate coils and magnets relative to each other, inducing an alternating potential difference and current.

6.

What energy transfer occurs when mechanical movement is used to generate electrical energy by electromagnetic induction?

Mechanical energy is transferred into electrical energy.

13.2 Recall the factors that affect the size and direction of an induced potential difference, and describe how the magnetic field produced opposes the original change

1.

What factors affect the size of an induced potential difference?

The speed of relative movement, the strength of the magnetic field and the number of turns in the coil.

2.

How does increasing the speed of relative movement between a magnet and conductor affect the induced potential difference?

It increases it.

3.

How does increasing the number of turns in a coil affect the induced potential difference?

It increases it.

4.

How does increasing the strength of the magnetic field affect the induced potential difference?

It increases it.

5.

How does reversing the direction of relative movement affect the direction of the induced potential difference?

It reverses the direction of the induced potential difference and current.

6.

How does the magnetic field produced by an induced current oppose the original change?

It produces a magnetic field that opposes the change that caused the current to be induced.

13.3P Explain how electromagnetic induction is used in alternators to generate current which alternates in direction (a.c.) and in dynamos to generate direct current (d.c.)

1.

What is the purpose of an alternator?

To convert mechanical energy into electrical energy by producing an alternating current.

2.

How does electromagnetic induction generate an alternating current in an alternator?

Relative rotation between the magnetic field and coil changes the magnetic flux through the coil, inducing a current.

3.

Why does the direction of the induced current change repeatedly in an alternator?

As the coil or field rotates, the direction of the change in flux reverses.

4.

What is the purpose of a dynamo?

To convert mechanical energy into electrical energy by producing a direct current.

5.

How does a dynamo produce direct current?

It uses a split-ring commutator to reverse the connections to the external circuit every half-turn.

6.

What is the main difference between the electrical output of an alternator and a dynamo?

An alternator produces a.c.; a dynamo produces d.c.

13.4P Explain the action of the microphone in converting the pressure variations in sound waves into variations in current in electrical circuits, and the reverse effect as used in loudspeakers and headphones

1.

How does a microphone convert sound waves into an electrical signal?

Sound waves cause a diaphragm to vibrate, producing variations in the electrical signal.

2.

What causes the diaphragm of a microphone to move?

Variations in air pressure caused by the sound wave.

3.

How are pressure variations in sound waves converted into variations in current?

The diaphragm moves a coil in a magnetic field, causing electromagnetic induction.

4.

How does a loudspeaker convert electrical signals into sound?

An alternating signal causes a coil in a magnetic field to move, moving the diaphragm and producing sound waves.

5.

How does a headphone work in converting electrical signals into sound?

An electrical signal causes a small diaphragm or coil to vibrate, producing sound waves.

6.

What is the reverse process performed by a loudspeaker compared with a microphone?

A microphone converts sound into an electrical signal; a loudspeaker converts an electrical signal back into sound.

13.5 Explain how an alternating current in one circuit can induce a current in another circuit in a transformer

1.

How does an alternating current in the primary coil produce a current in the secondary coil of a transformer?

It produces a changing magnetic field in the core, which induces a potential difference across the secondary coil.

2.

Why is an alternating current required for electromagnetic induction in a transformer?

It produces a continuously changing magnetic field, needed to induce a potential difference.

3.

What happens to the magnetic field in the transformer core when the primary current alternates?

It continually changes direction and strength.

4.

How does the changing magnetic field produce a potential difference in the secondary coil?

It passes through the secondary coil and induces a potential difference across it.

5.

Why are the primary and secondary coils electrically separate in a transformer?

To prevent a direct electrical connection between the two circuits.

6.

How does a transformer transfer energy between two electrical circuits?

Through the changing magnetic field in the core.

13.6 Recall that a transformer can change the size of an alternating voltage

1.

What does a transformer do to an alternating voltage?

It increases or decreases its size.

2.

What type of voltage can a transformer change?

Alternating voltage.

3.

What is the difference between a step-up and a step-down transformer?

A step-up transformer increases the voltage; a step-down decreases it.

4.

What happens to the output voltage of a step-up transformer?

It is greater than the input voltage.

5.

What happens to the output voltage of a step-down transformer?

It is less than the input voltage.

6.

Why can a transformer not directly change a steady direct voltage?

A steady voltage does not produce a continuously changing magnetic field.

13.7P Use the turns ratio equation for transformers to calculate either the missing voltage or the missing number of turns: Ns/Np = Vs/Vp

1.

What equation relates the number of turns and voltages in a transformer?

Ns/Np = Vs/Vp.

2.

A transformer has 500 primary turns and 2000 secondary turns. If the primary voltage is 12 V, calculate the secondary voltage.

Vs = (2000/500) × 12 = 48 V.

3.

A transformer has 1000 primary turns and 250 secondary turns. If the primary voltage is 240 V, calculate the secondary voltage.

Vs = (250/1000) × 240 = 60 V.

4.

A transformer has 600 primary turns and 1200 secondary turns and produces a secondary voltage of 20 V. Calculate the primary voltage.

Vp = 20 ÷ (1200/600) = 10 V.

5.

A transformer has a primary voltage of 230 V and a secondary voltage of 46 V. If the primary coil has 1000 turns, calculate the number of secondary turns.

Ns = (46/230) × 1000 = 200 turns.

6.

A transformer has 400 secondary turns and a primary voltage of 120 V. If the secondary voltage is 24 V, calculate the number of primary turns.

Np = 400 ÷ (24/120) = 2000 turns.

13.8 Explain why, in the national grid, electrical energy is transferred at high voltages from power stations, and then transferred at lower voltages in each locality for domestic uses as it improves the efficiency by reducing heat loss in transmission lines

1.

Why is electrical energy transmitted through the national grid at high voltages?

To reduce the current needed for a given power transfer, reducing energy loss as heat.

2.

How does increasing the transmission voltage affect the current for a given power transfer?

It decreases the current, since P = I × V.

3.

Why does a lower current reduce heating in transmission lines?

Power dissipated is proportional to I²R, so a smaller current greatly reduces heat loss.

4.

How does electrical resistance cause energy to be dissipated as heat in transmission lines?

Resistance in the cables transfers electrical energy into thermal energy.

5.

Why are lower voltages used for domestic electrical supplies?

They are safer and suitable for domestic appliances.

6.

How does high-voltage transmission improve the efficiency of the national grid?

It reduces current and therefore heat loss in the cables.

13.9 Explain where and why step-up and step-down transformers are used in the transmission of electricity in the national grid

1.

Where are step-up transformers used in the national grid?

At power stations, before electricity enters the transmission network.

2.

Why are step-up transformers used near power stations?

To increase the voltage, reducing the current and energy losses during transmission.

3.

Where are step-down transformers used in the national grid?

At substations closer to where electricity is used.

4.

Why are step-down transformers used before electricity reaches homes?

To reduce the voltage to a safer level for domestic and other users.

5.

How does a step-up transformer help reduce energy losses during transmission?

It reduces the current needed for a given power, reducing heat loss.

6.

How do step-up and step-down transformers work together in the national grid?

Step-up transformers increase voltage for efficient transmission; step-down transformers reduce it before use.

13.10 Use the power equation (for transformers with 100% efficiency): Vp × Ip = Vs × Is

1.

What equation relates the input and output power of an ideal transformer?

Vp × Ip = Vs × Is.

2.

An ideal transformer has a primary voltage of 240 V and a primary current of 5 A. If the secondary voltage is 60 V, calculate the secondary current.

Is = (240 × 5) ÷ 60 = 20 A.

3.

An ideal transformer has a primary voltage of 230 V and a primary current of 2 A. If the secondary current is 10 A, calculate the secondary voltage.

Vs = (230 × 2) ÷ 10 = 46 V.

4.

An ideal transformer has a secondary voltage of 12 V and a secondary current of 20 A. If the primary voltage is 240 V, calculate the primary current.

Ip = (12 × 20) ÷ 240 = 1 A.

5.

An ideal transformer has a primary voltage of 400 V and a primary current of 3 A. Calculate the secondary current if the secondary voltage is 40 V.

Is = (400 × 3) ÷ 40 = 30 A.

6.

Why does an ideal transformer have equal input and output power?

It has 100% efficiency, so no energy is lost.

13.11P Explain the advantages of power transmission in high-voltage cables, using the equations in 10.29, 10.31, 13.7P and 13.10

1.

Why does transmitting electrical power at high voltage reduce the current in transmission cables?

For a fixed power, increasing voltage decreases current, since P = I × V.

2.

Using P = I × V, how does increasing voltage allow the current to decrease for a fixed power transfer?

I = P/V, so for a fixed P, increasing V causes I to decrease.

3.

Using P = I² × R, why does reducing current greatly reduce the power dissipated as heat in cables?

Power dissipated is proportional to the square of the current.

4.

How does the transformer turns ratio allow the voltage to be increased before transmission?

A step-up transformer with more secondary turns than primary turns produces a higher secondary voltage.

5.

How does a step-down transformer allow the voltage to be reduced after transmission?

It has fewer turns on the secondary coil than on the primary coil.

6.

Explain how high-voltage transmission reduces energy loss and improves the efficiency of the national grid.

A step-up transformer increases voltage, reducing current and therefore heat loss according to P = I²R, so less energy is wasted.

14.1 Use a simple kinetic theory model to explain the different states of matter (solids, liquids and gases) in terms of the movement and arrangement of particles

1.

How are particles arranged in a solid?

Closely packed in a regular arrangement.

2.

How do particles move in a solid?

They vibrate about fixed positions.

3.

How are particles arranged in a liquid?

Close together but arranged irregularly.

4.

How do particles move in a liquid?

They move around and can slide past one another.

5.

How are particles arranged and how do they move in a gas?

Far apart, moving rapidly in random directions.

6.

How does the kinetic theory model explain the differences between solids, liquids and gases?

Solids have closely packed vibrating particles, liquids have closely packed moving particles, and gases have widely spaced rapidly moving particles.

14.2 Recall and use the equation: density (kilogram per cubic metre, kg/m³) = mass (kilogram, kg) ÷ volume (cubic metre, m³) ρ = m/V

1.

What equation is used to calculate density?

ρ = m/V.

2.

What is the SI unit of density?

kg/m³.

3.

A block has a mass of 600 kg and a volume of 0.5 m³. Calculate its density.

ρ = 600 ÷ 0.5 = 1200 kg/m³.

4.

A substance has a density of 800 kg/m³ and a volume of 2 m³. Calculate its mass.

m = 800 × 2 = 1600 kg.

5.

An object has a mass of 4 kg and a density of 2000 kg/m³. Calculate its volume.

V = 4 ÷ 2000 = 0.002 m³.

6.

A liquid has a mass of 1.5 kg and a volume of 0.002 m³. Calculate its density.

ρ = 1.5 ÷ 0.002 = 750 kg/m³.

14.3 Core Practical: Investigate the densities of solid and liquids

1.

How can the density of a regularly shaped solid be determined experimentally?

Measure its mass and dimensions to calculate volume, then ρ = m/V.

2.

How can the volume of an irregular solid be measured experimentally?

Measure the increase in volume when it is submerged in a measuring cylinder.

3.

How can the density of a liquid be determined experimentally?

Measure the mass of a known volume of liquid and calculate ρ = m/V.

4.

What measurements are required to calculate the density of a solid?

Its mass and volume.

5.

Why should measurements be repeated when determining density experimentally?

To calculate a mean and reduce the effect of random errors.

6.

How can a density experiment be improved to reduce uncertainty?

Repeat measurements, use suitable equipment and avoid parallax errors.

14.4 Explain the differences in density between the different states of matter in terms of the arrangements of the atoms or molecules

1.

Why are solids generally denser than gases?

Their particles are much closer together.

2.

How does the spacing between particles affect density?

Greater spacing means fewer particles occupy a given volume, giving lower density.

3.

Why are particles in a liquid generally closer together than particles in a gas?

Liquids have a generally higher density than gases.

4.

How does the arrangement of particles in a solid affect its density?

The closely packed arrangement means a large mass occupies a relatively small volume.

5.

Why can substances have different densities in different states?

Changing state changes the arrangement and spacing of particles.

6.

How does the particle model explain the generally lower density of gases?

Gas particles are widely separated, so a given mass occupies a large volume.

14.5 Describe that when substances melt, freeze, evaporate, boil, condense or sublimate mass is conserved and that these physical changes differ from some chemical changes because the material recovers its original properties if the change is reversed

1.

What happens to mass when a substance changes state?

It is conserved.

2.

What is the difference between melting and freezing?

Melting changes solid to liquid; freezing changes liquid to solid.

3.

What is the difference between evaporation and boiling?

Evaporation occurs at the surface and can occur below boiling point; boiling occurs throughout the liquid at its boiling point.

4.

What is condensation?

The change from a gas to a liquid.

5.

What is sublimation?

The change directly from a solid to a gas.

6.

Why are changes of state classified as physical changes rather than chemical changes?

No new substance is formed and the original properties can be recovered when reversed.

14.6 Explain how heating a system will change the energy stored within the system and raise its temperature or produce changes of state

1.

What happens to the energy stored in a system when it is heated?

It increases.

2.

How can heating a substance increase its temperature?

It increases the average kinetic energy of the particles.

3.

Why can heating a substance cause a change of state instead of increasing its temperature?

The energy changes the arrangement or separation of particles instead.

4.

What happens to the particles' energy when a substance is heated?

It increases their kinetic energy or changes their separation and arrangement.

5.

Why does the temperature remain constant during a change of state?

Energy is used to overcome forces between particles rather than increasing kinetic energy.

6.

How can energy supplied to a system be stored without increasing its temperature?

By changing the arrangement or separation of particles during a change of state.

14.7 Define the terms specific heat capacity and specific latent heat and explain the differences between them

1.

What is meant by specific heat capacity?

The energy required to raise the temperature of 1 kg of a substance by 1 °C.

2.

What is meant by specific latent heat?

The energy required to change the state of 1 kg of a substance without changing its temperature.

3.

What is the difference between specific heat capacity and specific latent heat?

Specific heat capacity relates to a temperature change; specific latent heat relates to a change of state at constant temperature.

4.

What happens to temperature when energy is transferred according to specific heat capacity?

It increases.

5.

What happens to temperature when energy is transferred as specific latent heat?

It remains constant.

6.

What does a high specific heat capacity mean about the energy required to increase a substance's temperature?

A large amount of energy is required.

14.8 Use the equation: change in thermal energy (joule, J) = mass (kilogram, kg) × specific heat capacity (joule per kilogram degree Celsius, J/kg °C) × change in temperature (degree Celsius, °C) ΔQ = m × c × Δθ

1.

What equation is used to calculate a change in thermal energy?

ΔQ = m × c × Δθ.

2.

What does c represent in the equation ΔQ = m × c × Δθ?

The specific heat capacity of the substance.

3.

Calculate the thermal energy needed to heat 2 kg of water by 10 °C if its specific heat capacity is 4200 J/kg °C.

ΔQ = 2 × 4200 × 10 = 84,000 J.

4.

A 3 kg substance gains 18,000 J of thermal energy and its temperature rises by 20 °C. Calculate its specific heat capacity.

c = 18,000 ÷ (3 × 20) = 300 J/kg °C.

5.

A material has a specific heat capacity of 500 J/kg °C. How much energy is required to raise 4 kg of it by 15 °C?

ΔQ = 4 × 500 × 15 = 30,000 J.

6.

A 2 kg substance with a specific heat capacity of 1000 J/kg °C receives 12,000 J of thermal energy. Calculate its temperature increase.

Δθ = 12,000 ÷ (2 × 1000) = 6 °C.

14.9 Use the equation: thermal energy for a change of state (joule, J) = mass (kilogram, kg) × specific latent heat (joule per kilogram, J/kg) Q = m × L

1.

What equation is used to calculate the thermal energy required for a change of state?

Q = m × L.

2.

What does L represent in the equation Q = m × L?

The specific latent heat of the substance.

3.

Calculate the energy required to melt 0.5 kg of a substance with a specific latent heat of 200,000 J/kg.

Q = 0.5 × 200,000 = 100,000 J.

4.

A substance absorbs 600,000 J during a change of state and has a specific latent heat of 300,000 J/kg. Calculate its mass.

m = 600,000 ÷ 300,000 = 2 kg.

5.

A 2 kg sample absorbs 800,000 J during a change of state. Calculate its specific latent heat.

L = 800,000 ÷ 2 = 400,000 J/kg.

6.

Why does the temperature remain constant while energy is transferred during a change of state?

The energy changes the arrangement or separation of particles rather than their kinetic energy.

14.10 Explain ways of reducing unwanted energy transfer through thermal insulation

1.

How does thermal insulation reduce unwanted energy transfer?

It reduces the rate of conduction, convection or radiation.

2.

Why does trapped air reduce thermal energy transfer?

Trapped air is a poor conductor and reduces convection.

3.

How can the thickness of insulation affect the rate of thermal energy transfer?

Increasing thickness generally decreases the rate of transfer.

4.

How can loft insulation reduce energy transfer from a building?

It traps air and reduces transfer through the roof.

5.

How can double glazing reduce energy transfer through windows?

It traps an insulating layer of air or gas between two panes.

6.

Why is reducing unwanted thermal energy transfer useful in buildings?

It helps buildings retain thermal energy and reduces energy used for heating.

14.11 Core Practical: Investigate the properties of water by determining the specific heat capacity of water and obtaining a temperature-time graph for melting ice

1.

How can the specific heat capacity of water be determined experimentally?

Measure the mass of water, use a heater of known power, measure the temperature rise over a measured time.

2.

What measurements are needed to calculate the specific heat capacity of water?

Mass of water, initial and final temperatures, power supplied and heating time.

3.

Why should the power supplied to the water be measured or controlled?

It determines the rate of energy transfer, allowing energy transferred to be calculated.

4.

How can a temperature-time graph be obtained while ice melts?

Measure temperature at regular time intervals while heating and plot against time.

5.

What feature of a temperature-time graph indicates that ice is undergoing a change of state?

A horizontal section where temperature remains constant.

6.

What practical methods can reduce heat loss when determining the specific heat capacity of water?

Using insulation, a lid and suitable apparatus.

14.12 Explain the pressure of a gas in terms of the motion of its particles

1.

Why does a gas exert pressure on the walls of its container?

Its particles collide with the walls.

2.

What happens when gas particles collide with the walls of their container?

Momentum is transferred to the walls, exerting a force.

3.

How does the motion of gas particles produce a force on the container walls?

The change in momentum during collisions produces a force.

4.

Why do gas particles exert pressure in all directions?

They move randomly in all directions, colliding with all surfaces.

5.

What happens to gas pressure if the frequency of particle collisions with the walls increases?

Pressure increases.

6.

How does the kinetic theory explain gas pressure?

It is caused by the random motion of gas particles and their collisions with the container walls.

14.13 Explain the effect of changing the temperature of a gas on the velocity of its particles and hence on the pressure produced by a fixed mass of gas at constant volume (qualitative only)

1.

What happens to the average velocity of gas particles when the temperature increases?

It increases.

2.

Why do faster-moving gas particles produce more frequent or more energetic collisions?

They travel and collide with the walls more often and with greater force.

3.

What happens to the pressure of a fixed mass of gas when its temperature increases at constant volume?

It increases.

4.

What happens to particle velocity when the temperature of a gas decreases?

It decreases.

5.

Why does cooling a gas at constant volume reduce its pressure?

Collisions with the walls become less frequent and less energetic.

6.

How does increasing temperature affect the force exerted by gas particles on the container walls?

It increases the force, due to more frequent and energetic collisions.

14.14 Describe the term absolute zero, −273 °C, in terms of the lack of movement of particles

1.

What is absolute zero in degrees Celsius?

−273 °C.

2.

What does absolute zero represent in terms of particle motion?

The theoretical temperature at which particles have no movement.

3.

What happens to the movement of particles as a substance approaches absolute zero?

It decreases.

4.

Why is absolute zero associated with the minimum possible thermal energy?

Particle motion is at its minimum.

5.

What temperature is equivalent to absolute zero on the Celsius scale?

−273 °C.

6.

How does the particle model describe matter at absolute zero?

Particles have no movement.

14.15 Convert between the kelvin and Celsius scales

1.

What is the relationship between temperature in kelvin and temperature in degrees Celsius?

Kelvin = °C + 273.

2.

Convert 27 °C to kelvin.

27 + 273 = 300 K.

3.

Convert 300 K to degrees Celsius.

300 − 273 = 27 °C.

4.

Convert −73 °C to kelvin.

−73 + 273 = 200 K.

5.

Convert 100 K to degrees Celsius.

100 − 273 = −173 °C.

6.

What kelvin temperature corresponds to 0 °C?

273 K.

14.16P Explain that gases can be compressed or expanded by pressure changes

1.

What happens to the volume of a gas when external pressure is increased?

It decreases.

2.

Why can gases be compressed more easily than liquids and solids?

Their particles have large spaces between them.

3.

What happens to a gas when the external pressure is reduced?

It expands.

4.

How does the spacing between gas particles change when a gas is compressed?

It decreases.

5.

How does the spacing between gas particles change when a gas expands?

It increases.

6.

Why can changing pressure cause a gas to compress or expand?

Changing external pressure changes the forces acting on the gas.

14.17P Explain that the pressure of a gas produces a net force at right angles to any surface

1.

How does gas pressure produce a force on a surface?

Particle collisions with the surface produce a force.

2.

In what direction does the force from gas pressure act on a surface?

At right angles (perpendicular) to the surface.

3.

Why does gas pressure act at right angles to a surface?

Particle collisions transfer momentum perpendicular to the surface.

4.

What happens to the force on a surface if the gas pressure increases?

It increases.

5.

How does the area of a surface affect the total force produced by a given gas pressure?

A larger area produces a greater total force for the same pressure.

6.

How is the force produced by gas pressure different from the random motion of individual gas particles?

Individual particles move randomly, but their many collisions produce a net perpendicular force.

14.18P Explain the effect of changing the volume of a gas on the rate at which its particles collide with the walls of its container and hence on the pressure produced by a fixed mass of gas at constant temperature

1.

What happens to the frequency of particle collisions with the container walls when the volume of a gas decreases?

It increases.

2.

Why does compressing a gas increase its pressure at constant temperature?

The collision rate with the walls increases.

3.

What happens to the collision rate when the volume of a gas increases?

It decreases.

4.

Why does expanding a gas reduce its pressure at constant temperature?

The collision rate with the walls decreases.

5.

How does the distance particles travel between collisions with the container walls change when volume decreases?

It decreases, so particles have less distance to travel before colliding.

6.

How does the particle model explain the inverse relationship between gas pressure and volume at constant temperature?

Decreasing volume increases collision rate and pressure; increasing volume decreases them.

14.19P Use the equation: P₁ × V₁ = P₂ × V₂ to calculate pressure or volume for gases of fixed mass at constant temperature

1.

What equation relates the pressure and volume of a fixed mass of gas at constant temperature?

P₁ × V₁ = P₂ × V₂.

2.

A gas has a pressure of 100 kPa and a volume of 4 m³. If its volume decreases to 2 m³, calculate its new pressure.

P₂ = (100 × 4) ÷ 2 = 200 kPa.

3.

A gas has a pressure of 200 kPa and a volume of 3 m³. If its pressure decreases to 100 kPa, calculate its new volume.

V₂ = (200 × 3) ÷ 100 = 6 m³.

4.

A gas has an initial pressure of 150 kPa and volume of 2 m³. Its final volume is 5 m³. Calculate its final pressure.

P₂ = (150 × 2) ÷ 5 = 60 kPa.

5.

A gas has an initial pressure of 80 kPa and volume of 6 m³. Its final pressure is 120 kPa. Calculate its final volume.

V₂ = (80 × 6) ÷ 120 = 4 m³.

6.

A gas has a volume of 0.5 m³ at a pressure of 400 kPa. What volume will it occupy at a pressure of 100 kPa?

V₂ = (400 × 0.5) ÷ 100 = 2 m³.

14.20P Explain why doing work on a gas can increase its temperature, including a bicycle pump

1.

How can doing work on a gas increase its temperature?

It transfers energy to the gas, increasing its internal energy.

2.

What happens to the internal energy of a gas when work is done on it?

It increases.

3.

Why can compressing a gas increase its temperature?

The energy of its particles increases.

4.

How does a bicycle pump demonstrate that doing work on a gas can increase its temperature?

Rapid pumping compresses the air, causing the pump and air to warm.

5.

What happens to the particles of a gas when it is compressed rapidly?

Their energy increases.

6.

How does the energy transfer during compression explain the increase in gas temperature?

Mechanical energy is transferred to the gas as internal energy, increasing particle energy and temperature.

15.1 Explain, using springs and other elastic objects, that stretching, bending or compressing an object requires more than one force

1.

Why are at least two forces required to stretch a spring?

So the forces act on different parts of the object to change its shape.

2.

What happens to a spring when two opposing forces pull on its ends?

It stretches.

3.

How can two forces cause an object to bend?

Forces acting in opposite directions at different positions can produce a turning effect that changes shape.

4.

How can forces be used to compress an object?

Opposing forces can push different parts of an object towards each other.

5.

What happens to the shape of an object when opposing forces act on it?

It changes shape, becoming longer, shorter, curved or compressed.

6.

Why does stretching, bending or compressing an object require forces acting in different directions?

Forces at different points or in different directions are needed to change shape.

15.2 Describe the difference between elastic and inelastic distortion

1.

What is meant by elastic distortion?

A change in shape that is reversed when the deforming forces are removed.

2.

What is meant by inelastic distortion?

A permanent change in shape that is not completely reversed when the forces are removed.

3.

What happens to an object after an elastic distortion when the forces are removed?

It returns to its original shape.

4.

What happens to an object after an inelastic distortion when the forces are removed?

It remains permanently deformed.

5.

How can you determine experimentally whether a distortion is elastic?

Remove the applied force and observe whether the object returns to its original shape.

6.

What happens when an object is stretched beyond its elastic limit?

It undergoes permanent deformation and does not return fully to its original shape.

15.3 Recall and use the equation for linear elastic distortion including calculating the spring constant: force exerted on a spring (newton, N) = spring constant (newton per metre, N/m) × extension (metre, m) F = k × x

1.

What equation relates force, spring constant and extension for a linearly elastic spring?

F = k × x.

2.

What is the unit of spring constant?

N/m.

3.

A spring has a spring constant of 200 N/m and an extension of 0.05 m. Calculate the force.

F = 200 × 0.05 = 10 N.

4.

A spring experiences a force of 12 N and extends by 0.03 m. Calculate its spring constant.

k = 12 ÷ 0.03 = 400 N/m.

5.

A spring has a spring constant of 150 N/m and experiences a force of 6 N. Calculate its extension.

x = 6 ÷ 150 = 0.04 m.

6.

A spring extends by 0.08 m when a force of 16 N is applied. Calculate the spring constant.

k = 16 ÷ 0.08 = 200 N/m.

15.4 Use the equation to calculate the work done in stretching a spring: energy transferred in stretching (joules, J) = 0.5 × spring constant (newton per metre, N/m) × (extension (metre, m))² E = 0.5 × k × x²

1.

What equation is used to calculate the energy transferred when stretching a spring?

E = 0.5 × k × x².

2.

A spring has a spring constant of 100 N/m and is extended by 0.2 m. Calculate the energy transferred.

E = 0.5 × 100 × 0.2² = 2 J.

3.

A spring has a spring constant of 250 N/m and is extended by 0.04 m. Calculate the energy transferred.

E = 0.5 × 250 × 0.04² = 0.2 J.

4.

A spring stores 9 J of energy when extended by 0.3 m. Calculate its spring constant.

k = (2 × 9) ÷ 0.3² = 200 N/m.

5.

A spring with a spring constant of 400 N/m stores 8 J of energy. Calculate its extension.

x = √((2 × 8) ÷ 400) = 0.2 m.

6.

How does doubling the extension affect the energy transferred to a spring, assuming it remains within the linear elastic region?

The energy increases by a factor of 4.

15.5 Describe the difference between linear and non-linear relationships between force and extension

1.

What is meant by a linear relationship between force and extension?

Force is directly proportional to extension.

2.

What would the force-extension graph of a linearly elastic spring look like?

A straight line with a constant gradient, through the origin if there is no initial extension.

3.

What is meant by a non-linear relationship between force and extension?

Force is not directly proportional to extension.

4.

How can a force-extension graph be used to identify a non-linear relationship?

A curved graph indicates a non-linear relationship.

5.

What does a constant gradient on a force-extension graph indicate?

The spring constant is constant and force is proportional to extension.

6.

Why might a spring have a non-linear relationship between force and extension?

The stiffness of the object may change as it is stretched.

15.6 Core Practical: Investigate the extension and work done when applying forces to a spring

1.

How can the extension of a spring be measured experimentally?

Measure the original length, apply a known force, measure the new length, and find extension = new length − original length.

2.

What measurements are needed to investigate the relationship between force and extension?

The applied force and the extension of the spring.

3.

How can the force applied to a spring be varied during the experiment?

Add known masses to the spring and use their weight to provide different forces.

4.

How can the work done in stretching a spring be determined?

Using E = 0.5 × k × x², or the area under the force-extension graph.

5.

Why should the spring not be stretched beyond its elastic limit?

It can cause permanent deformation, making results unreliable.

6.

How can a force-extension graph be used to analyse the results of the spring experiment?

A straight-line section indicates a linear relationship; a curved section indicates a non-linear relationship.

15.7P Explain why atmospheric pressure varies with height above the Earth's surface with reference to a simple model of the Earth's atmosphere

1.

What happens to atmospheric pressure as height above Earth's surface increases?

It decreases.

2.

Why is atmospheric pressure greatest near Earth's surface?

There is more air above a location near the surface, so its weight produces greater pressure.

3.

How does the number of air particles above a location affect atmospheric pressure?

More particles above a location means greater weight of air and therefore greater pressure.

4.

Why does the density of the atmosphere generally decrease with increasing height?

The air becomes less compressed at greater heights.

5.

Why does atmospheric pressure decrease at higher altitudes?

There is less air above a point at higher altitude, so the weight of air above it is smaller.

6.

How does a simple particle model of the atmosphere explain the variation of pressure with height?

At greater heights there are fewer particles above a given point, so the weight of air above and pressure decrease.

15.8P Describe the pressure in a fluid as being due to the fluid and atmospheric pressure

1.

What contributes to the pressure experienced by an object beneath the surface of a liquid?

Atmospheric pressure plus the pressure caused by the fluid above the object.

2.

What is meant by atmospheric pressure?

The pressure exerted by the atmosphere on surfaces.

3.

How does the weight of a fluid contribute to pressure?

The weight of fluid above a point produces pressure on that point.

4.

Why does a liquid exert pressure on objects immersed in it?

Its particles exert forces on surfaces and the fluid has weight.

5.

How do atmospheric pressure and liquid pressure combine below the surface of a liquid?

The total pressure is atmospheric pressure plus the pressure due to the fluid.

6.

Why is the pressure in a liquid greater than atmospheric pressure alone at depth?

The fluid itself produces additional pressure due to the weight of the fluid above.

15.9P Recall that the pressure in fluids causes a force normal to any surface

1.

What direction does the force caused by fluid pressure act on a surface?

Perpendicular to the surface.

2.

What does normal mean when describing a force acting on a surface?

Perpendicular to the surface.

3.

Why does fluid pressure produce a force perpendicular to a surface?

Fluid pressure acts equally in all directions.

4.

How does fluid pressure act on the walls of a container?

It produces forces perpendicular to the walls.

5.

What happens to the force on a surface if the fluid pressure increases?

It increases.

6.

How does the direction of the pressure force change if the orientation of the surface changes?

It remains perpendicular to the surface, so its direction changes with the surface's orientation.

15.10P Explain how pressure is related to force and area, using appropriate examples

1.

How does increasing the force on a fixed area affect pressure?

Pressure increases.

2.

How does increasing the area over which a fixed force acts affect pressure?

Pressure decreases.

3.

Why do sharp objects produce high pressures?

They have a small contact area, so a given force produces a high pressure.

4.

Why do wide tyres reduce the pressure exerted on the ground?

They spread the force over a larger area.

5.

Why can a person standing on one foot exert greater pressure on the ground than when standing on two feet?

The same weight acts over a smaller area.

6.

How can the same force produce different pressures depending on the area over which it acts?

Pressure depends on both force and area.

15.11P Recall and use the equation: pressure (pascal, Pa) = force normal to surface (newton, N) ÷ area of surface (square metre, m²) P = F/A

1.

What equation is used to calculate pressure?

P = F ÷ A.

2.

What is the SI unit of pressure?

The pascal (Pa).

3.

A force of 500 N acts normally on an area of 2 m². Calculate the pressure.

P = 500 ÷ 2 = 250 Pa.

4.

A pressure of 20,000 Pa acts on an area of 0.5 m². Calculate the normal force.

F = 20,000 × 0.5 = 10,000 N.

5.

A force of 800 N produces a pressure of 40,000 Pa. Calculate the area.

A = 800 ÷ 40,000 = 0.02 m².

6.

A force of 120 N acts normally over an area of 0.03 m². Calculate the pressure.

P = 120 ÷ 0.03 = 4000 Pa.

15.12P Describe how pressure in fluids increases with depth and density

1.

What happens to liquid pressure as depth increases?

It increases.

2.

What happens to liquid pressure when the density of the liquid increases?

It increases.

3.

Why is pressure greater at the bottom of a liquid container than near the surface?

There is more fluid above the point, producing a greater pressure.

4.

Which produces greater pressure at the same depth: a high-density liquid or a low-density liquid?

A high-density liquid.

5.

How does the weight of fluid above a point affect pressure at that point?

Greater weight above a point produces greater pressure.

6.

How do depth and density affect the pressure within a fluid?

Pressure increases with both depth and fluid density.

15.13P Explain why the pressure in liquids varies with density and depth

1.

Why does pressure in a liquid increase with depth?

Increasing depth increases the weight of liquid above a point.

2.

Why does a denser liquid produce greater pressure at the same depth?

It has more mass and therefore greater weight for the same volume.

3.

How does the mass of liquid above a point affect pressure?

Increasing mass increases the force due to weight and therefore pressure.

4.

Why does increasing depth increase the weight of liquid above a point?

There is a greater column of liquid above the point.

5.

Why would two liquids at the same depth produce different pressures if they have different densities?

A denser liquid has greater mass for the same volume.

6.

How does the particle model of a liquid help explain why pressure depends on depth and density?

The liquid has weight; a greater depth or density means more weight above the point, increasing pressure.

15.14P Use the equation to calculate the magnitude of the pressure in liquids and calculate the differences in pressure at different depths in a liquid: pressure due to a column of liquid (pascal, Pa) = height of column (metre, m) × density of liquid (kilogram per cubic metre, kg/m³) × gravitational field strength (newton per kilogram, N/kg) P = h × ρ × g

1.

What equation is used to calculate the pressure due to a column of liquid?

P = h × ρ × g.

2.

Calculate the pressure at a depth of 5 m in water with density 1000 kg/m³, taking g = 10 N/kg.

P = 5 × 1000 × 10 = 50,000 Pa.

3.

A liquid has a density of 800 kg/m³ and a depth of 4 m. Calculate the pressure due to the liquid, taking g = 10 N/kg.

P = 4 × 800 × 10 = 32,000 Pa.

4.

A liquid produces a pressure of 30,000 Pa at a depth of 3 m. Taking g = 10 N/kg, calculate the liquid's density.

ρ = 30,000 ÷ (3 × 10) = 1000 kg/m³.

5.

Water has a density of 1000 kg/m³. Calculate the difference in pressure between depths of 2 m and 7 m, taking g = 10 N/kg.

ΔP = 5 × 1000 × 10 = 50,000 Pa.

6.

A liquid has a density of 1200 kg/m³. Calculate the depth required to produce a pressure of 48,000 Pa, taking g = 10 N/kg.

h = 48,000 ÷ (1200 × 10) = 4 m.

15.15P Explain why an object in a fluid is subject to an upwards force (upthrust) and relate this to examples including objects that are fully immersed in a fluid (liquid or gas) or partially immersed in a liquid

1.

What is meant by upthrust?

An upwards force exerted by a fluid on an object immersed in it.

2.

Why does a fluid exert an upwards force on an immersed object?

Fluid pressure increases with depth, so pressure on the bottom of the object is greater than on the top.

3.

Why is the pressure on the bottom of a fully immersed object greater than the pressure on its top?

The bottom is at a greater depth, where fluid pressure is greater.

4.

How does the pressure difference between the top and bottom of an object produce upthrust?

The greater pressure on the bottom produces a larger upward force than the downward force on top.

5.

Why does a partially immersed object also experience an upthrust?

The fluid pressure acting on the submerged part produces an upward force.

6.

How can upthrust act on an object immersed in a gas as well as an object immersed in a liquid?

Gases also exert pressure, and a pressure difference between surfaces can produce an upward force.

15.16P Recall that the upthrust is equal to the weight of fluid displaced

1.

What is the relationship between upthrust and the weight of displaced fluid?

Upthrust equals the weight of fluid displaced.

2.

What is meant by the fluid displaced by an immersed object?

The fluid that would have occupied the volume taken up by the immersed part of the object.

3.

An object displaces 0.02 m³ of water with density 1000 kg/m³. Taking g = 10 N/kg, calculate the upthrust.

Mass = 1000 × 0.02 = 20 kg; weight = 20 × 10 = 200 N; upthrust = 200 N.

4.

An object experiences an upthrust of 50 N. What is the weight of the fluid it displaces?

50 N.

5.

How does the volume of fluid displaced affect the upthrust?

Increasing the volume displaced increases the upthrust.

6.

Why does an object displacing more fluid experience a greater upthrust?

A greater volume of displaced fluid has a greater weight.

15.17P Explain how the factors (upthrust, weight, density of fluid) influence whether an object will float or sink

1.

What happens when the weight of an object is greater than its upthrust?

The object sinks.

2.

What happens when the upthrust on an object is greater than its weight?

The object accelerates upwards.

3.

What condition must be satisfied for an object to float in equilibrium?

The upthrust must equal its weight.

4.

How does the density of an object compared with the density of a fluid affect whether it floats or sinks?

A lower average density than the fluid tends to float; a greater average density tends to sink.

5.

Why does an object with a lower average density than the fluid tend to float?

It has less weight for its volume and can displace enough fluid for the upthrust to balance its weight.

6.

Why does an object with a greater average density than the fluid tend to sink?

It cannot displace enough fluid to produce an upthrust equal to its weight before becoming fully submerged.

Physics

Edexcel GCSE Triple Science: Physics

Topic 1 – Key concepts of physics

1.1 Recall and use the SI unit for physical quantities, as listed in Appendix 3

1.2 Recall and use multiples and sub-multiples of units, including giga (G), mega (M), kilo (k), centi (c), milli (m), micro (μ) and nano (n)

1.3 Be able to convert between different units, including hours to seconds

1.4 Use significant figures and standard form where appropriate

Topic 2 – Motion and forces

2.1 Explain that a scalar quantity has magnitude (size) but no specific direction

2.2 Explain that a vector quantity has both magnitude (size) and a specific direction

2.3 Explain the difference between vector and scalar quantities

2.4 Recall vector and scalar quantities, including: a displacement/distance b velocity/speed c acceleration d force e weight/mass f momentum g energy

2.5 Recall that velocity is speed in a stated direction

2.6 Recall and use the equations: a (average) speed (metre per second, m/s) = distance (metre, m) ÷ time (s) b distance travelled (metre, m) = average speed (metre per second, m/s) × time (s)

2.7 Analyse distance/time graphs including determination of speed from the gradient

2.8 Recall and use the equation: acceleration (metre per second squared, m/s²) = change in velocity (metre per second, m/s) ÷ time taken (second, s) (v − u) ÷ t = a

2.9 Use the equation: (final velocity)² − (initial velocity)² = 2 × acceleration × distance, v² − u² = 2 × a × x

2.10 Analyse velocity/time graphs to: a compare acceleration from gradients qualitatively b calculate the acceleration from the gradient (for uniform acceleration only) c determine the distance travelled using the area between the graph line and the time axis (for uniform acceleration only)

2.11 Describe a range of laboratory methods for determining the speeds of objects such as the use of light gates

2.12 Recall some typical speeds encountered in everyday experience for wind and sound, and for walking, running, cycling and other transportation systems

2.13 Recall that the acceleration, g, in free fall is 10 m/s² and be able to estimate the magnitudes of everyday accelerations

2.14 Recall Newton's first law and use it in the following situations: a where the resultant force on a body is zero, i.e. the body is moving at a constant velocity or is at rest b where the resultant force is not zero, i.e. the speed and/or direction of the body change(s)

2.15 Recall and use Newton's second law as: force (newton, N) = mass (kilogram, kg) × acceleration (metre per second squared, m/s²) F = m × a

2.16 Define weight, recall and use the equation: weight (newton, N) = mass (kilogram, kg) × gravitational field strength (newton per kilogram, N/kg) W = m × g

2.17 Describe how weight is measured

2.18 Describe the relationship between the weight of a body and the gravitational field strength

2.19 Core Practical: Investigate the relationship between force, mass and acceleration by varying the masses added to trolleys

2.20 Explain that an object moving in a circular orbit at constant speed has a changing velocity (qualitative only)

2.21 Explain that for motion in a circle there must be a resultant force known as a centripetal force that acts towards the centre of the circle

2.22 Explain that inertial mass is a measure of how difficult it is to change the velocity of an object (including from rest) and know that it is defined as the ratio of force over acceleration

2.23 Recall and apply Newton's third law both to equilibrium situations and to collision interactions and relate it to the conservation of momentum in collisions

2.24 Define momentum, recall and use the equation: momentum (kilogram metre per second, kg m/s) = mass (kilogram, kg) × velocity (metre per second, m/s) p = m × v

2.25 Describe examples of momentum in collisions

2.26 Use Newton's second law as: force (newton, N) = change in momentum (kilogram metre per second, kg m/s) ÷ time (second, s) (mv − mu) ÷ t = F

2.27 Explain methods of measuring human reaction times and recall typical results

2.28 Recall that the stopping distance of a vehicle is made up of the sum of the thinking distance and the braking distance

2.30 Describe the factors affecting a driver's reaction time including drugs and distractions

2.31 Explain the dangers caused by large decelerations and estimate the forces involved in typical situations on a public road

2.32P Estimate how the distance required for a road vehicle to stop in an emergency varies over a range of typical speeds

2.33P Carry out calculations on work done to show the dependence of braking distance for a vehicle on initial velocity squared (work done to bring a vehicle to rest equals its initial kinetic energy)

Topic 3 – Conservation of energy

3.2 Recall and use the equation to calculate the amounts of energy associated with a moving object: kinetic energy (joule, J) = 1/2 × mass (kilogram, kg) × (speed)² ((metre/second)², (m/s)²) KE = 1/2 × m × v²

3.3 Draw and interpret diagrams to represent energy transfers

3.4 Explain what is meant by conservation of energy

3.6 Explain that where there are energy transfers in a closed system there is no net change to the total energy in that system

3.7 Explain that mechanical processes become wasteful when they cause a rise in temperature so dissipating energy in heating the surroundings

3.8 Explain, using examples, how in all system changes energy is dissipated so that it is stored in less useful ways

3.9 Explain ways of reducing unwanted energy transfer including through lubrication, thermal insulation

3.10 Describe the effects of the thickness and thermal conductivity of the walls of a building on its rate of cooling qualitatively

3.11 Recall and use the equation: efficiency = useful energy transferred by the device ÷ total energy supplied to the device

3.12 Explain how efficiency can be increased

3.13 Describe the main energy sources available for use on Earth (including fossil fuels, nuclear fuel, bio-fuel, wind, hydroelectricity, the tides and the Sun), and compare the ways in which both renewable and non-renewable sources are used

3.14 Explain patterns and trends in the use of energy resources

Topic 4 – Waves

4.1 Recall that waves transfer energy and information without transferring matter

4.2 Describe evidence that with water and sound waves it is the wave and not the water or air itself that travels

4.3 Define and use the terms frequency and wavelength as applied to waves

4.4 Use the terms amplitude, period, wave velocity and wavefront as applied to waves

4.5 Describe the difference between longitudinal and transverse waves by referring to sound, electromagnetic, seismic and water waves

4.6 Recall and use both the equations below for all waves: wave speed (metre/second, m/s) = frequency (hertz, Hz) × wavelength (metre, m) v = f × λ; wave speed (metre/second, m/s) = distance (metre, m) ÷ time (second, s) v = x ÷ t

4.7 Describe how to measure the velocity of sound in air and ripples on water surfaces

4.8P Calculate depth or distance from time and wave velocity

4.9P Describe the effects of a reflection b refraction c transmission d absorption of waves at material interfaces

4.10 Explain how waves will be refracted at a boundary in terms of the change of direction and speed

4.11 Recall that different substances may absorb, transmit, refract or reflect waves in ways that vary with wavelength

4.12P Describe the processes which convert wave disturbances between sound waves and vibrations in solids, and a explain why such processes only work over a limited frequency range b use this to explain the way the human ear works

4.13P Recall that sound with frequencies greater than 20 000 hertz, Hz, is known as ultrasound

4.14P Recall that sound with frequencies less than 20 hertz, Hz, is known as infrasound

4.15P Explain uses of ultrasound and infrasound, including a sonar b foetal scanning c exploration of the Earth's core

4.16P Describe how changes, if any, in velocity, frequency and wavelength, in the transmission of sound waves from one medium to another are inter-related

4.17 Core Practical: Investigate the suitability of equipment to measure the speed, frequency and wavelength of a wave in a solid and a fluid

Topic 5 – Light and the electromagnetic spectrum

5.1P Explain, with the aid of ray diagrams, reflection, refraction and total internal reflection (TIR), including the law of reflection and critical angle

5.2P Explain the difference between specular and diffuse reflection

5.3P Explain how colour of light is related to a differential absorption at surfaces b transmission of light through filters

5.4P Relate the power of a lens to its focal length and shape

5.5P Use ray diagrams to show the similarities and differences in the refraction of light by converging and diverging lenses

5.6P Explain the effects of different types of lens in producing real and virtual images

5.7 Recall that all electromagnetic waves are transverse, that they travel at the same speed in a vacuum

5.8 Explain, with examples, that all electromagnetic waves transfer energy from source to observer