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YOU MUST KEEP THIS BOOKLET TILL GCSE EXAMS

Physics Paper 1

Knowledge Questions Booklet (H)

Name:

Class:

2

Physics paper 1 Knowledge Questions

pg Topic Date 1 Date 2 Date 3

P1

3 Energy Stores and Systems 5 Kinetic and Potential Energy Stores 7 Specific Heat Capacity 11 Power 13 Reducing Unwanted Energy Transfers 15 Efficiency 17 Energy Resources 1 19 Energy Resources 2

P2

23 Current and Circuit Systems 25 Resistance and V = IR 27 Resistance and I-V Characteristics 29 Circuit Devices 31 Series and Parallel Circuits 33 Investigating Resistance 35 Electricity in the Home 37 Electrical Power 39 The National Grid

P3 41 Particle Model and Density of Materials 43 Internal Energy, Changes of State and Specific

Latent Heat

P4

45 Developing the Model of the Atom 47 Isotopes and Nuclear Radiation 49 Nuclear Equations 51 Half-Life 53 Irradiation and Contamination

What is the best way to use this knowledge question booklet?

Read the CGP guide first with the page number

On a lined piece of paper, answer all the questions in black pen (one worded answers) o Do not write answers on the booklet

Turnover and mark using green pen.

Add the date under ‘date 1’

Repeat the knowledge questions three times (space apart) to make sure you have mastered the content.

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Energy Stores and Systems p167 CGP Knowledge Questions

1 What is the scientific name given to a group of objects? Examples include a tennis racket that hits a tennis ball or a car that collides into another car.

2 What happens to the amount of matter or energy in a closed system? 3 What mnemonic is used to remember the eight energy stores? 4 Complete: When a ball is projected upwards, the energy in its __________ energy store increases. 5 Objects that are compressed have lots of energy in which store? 6 Batteries have lots of energy in which energy store? 7 What happens to the internal energy of the particles that form the surroundings every time work is

done? 8 What is meant by the phrase ‘energy is dissipated’? 9 Complete: When a tennis ball collides into a wall, its __________ energy store increases. 10 If a ball is dropped from a tall building, it will accelerate. What happens to the energy in the ball’s

gravitational energy store? 11 When a car slows down, energy in its kinetic energy store transfers into which energy store? Of

which object? 12 When water is boiled, energy is transferred from the kettle’s heating element to the water’s thermal

energy store. State the objects in this closed system. 13 What mnemonic is used to recall the four mechanisms by which energy can transfer? 14 Complete with the correct mechanism: When water is boiled, energy is transferred __________

from the kettle’s heating element to the water’s thermal energy store. Practice Questions

15 When wood burns: a State the initial energy store and the object in which the energy store is contained. b State the final energy store and the object in which the energy store is contained. c State the mechanism by which energy transfers.

16 As Tom Daley dives into a swimming pool: a State the initial energy store and the object in which the energy store is contained. b State the final energy store and the object in which the energy store is contained. c State the mechanism by which energy transfers.

17 Complete: 3,000 Joules of energy is transferred to lift an object up into the air. When the ball falls back down and reaches its highest speed, it has 2,700 Joules of energy in its kinetic energy store. ___ Joules of energy is dissipated into the surroundings.

18 The total energy in a closed system with a kettle’s heating element and water is 650 Joules. 500 Joules is transferred to the water for it to reach boiling point. ___ Joules remains stored in the kettle’s heating element.

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Energy Stores and Systems p167 CGP Knowledge Answers

1 What is the scientific name given to a group of objects? Examples include a tennis racket that hits a tennis ball or a car that collides into another car. System

2 What happens to the amount of matter or energy in a closed system? Remains the same 3 What mnemonic is used to remember the eight energy stores? These (thermal) kids (kinetic) can

(chemical) easily (elastic potential) master (magnetic) GCSE (gravitational potential) energy (electrostatic) names (nuclear).

4 Complete: When an object is projected upwards, the energy in its gravitational potential energy store increases.

5 Objects that are compressed have lots of energy in which store? Elastic potential energy store 6 Batteries have lots of energy in which energy store? Chemical energy store 7 What happens to the internal energy of the particles that form the surroundings every time work is

done? The internal energy of the particles that form the surroundings increases 8 What is meant by the phrase ‘energy is dissipated’? Energy is transferred to the surroundings in a

way that is not useful. 9 Complete: When a tennis ball collides into a wall, its elastic potential energy store increases. 10 If a ball is dropped from a tall building, it will accelerate. What happens to the energy in the ball’s

gravitational energy store? The energy transfers into the ball’s kinetic energy store 11 When a car slows down, energy in its kinetic energy store transfers into which energy store? Of

which object? Thermal energy store of the wheels and the surroundings 12 When water is boiled, energy is transferred from the kettle’s heating element to the water’s thermal

energy store. State the objects in this closed system. The kettle and the water 13 What mnemonic is used to recall the four mechanisms by which energy can transfer? Even

(electrically) robots (radiation/waves) have (heating) feelings (force) 14 Complete with the correct mechanism: When water is boiled, energy is transferred by heating from

the kettle’s heating element to the water’s thermal energy store. Practice Answers

15 When wood burns: a State the initial energy store and the object in which the energy store is contained. Chemical

energy store of the wood b State the final energy store and the object in which the energy store is contained. Thermal

energy store of the surroundings c State the mechanism by which energy transfers. By heating

16 As Tom Daley dives into a swimming pool: d State the initial energy store and the object in which the energy store is contained.

Gravitational potential energy store of Tom Daley e State the final energy store and the object in which the energy store is contained. Kinetic

energy store of Tom Daley f State the mechanism by which energy transfers. By a force (gravity)

17 Complete: 3,000 Joules of energy is transferred to lift an object up into the air. When the ball falls back down and reaches its highest speed, it has 2,700 Joules of energy in its kinetic energy store. 300 Joules of energy is dissipated into the surroundings.

18 The total energy in a closed system with a kettle’s heating element and water is 650 Joules. 500 Joules is transferred to the water for it to reach boiling point. 150 Joules remains stored in the kettle’s heating element.

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Kinetic and Potential Energy Stores p168 CGP Knowledge Questions

1 State the type of energy store that will contain energy if an object is moving. 2 What does the amount of energy in an object’s kinetic energy store depend on? 3 State the kinetic energy equation including units. 4 What energy store of an object will be increased when it is lifted upwards. 5 State the equation, including units, used to calculate the change in the gravitational potential

energy store of an object. 6 What is the relationship between the gravitational potential energy (gpe) store and kinetic energy

(ke) store of a falling object when there is no air resistance? 7 What energy store increases when an object is stretched or squashed? 8 State the equation used, including the units, to find the energy in the elastic potential energy store

of an object. 9 We can only use the equation above when an object’s __________ is not exceeded.

Practice Questions

10 Calculate the amount of kinetic energy in the kinetic energy stores of the following objects: a A car with a mass of 1000 kg travelling at 10 m/s. b A ping pong ball with a mass of 50 g travelling at 3 m/s. c A runner with a mass of 80 kg running at 2 m/s.

11 Calculate the mass of a car with a kinetic energy store of 35,000 J travelling at 10 m/s. 12 Calculate the speed a car with a kinetic energy store of 35,000 J and a mass of 800 kg. 13 Calculate the mass a football with 8 J of gravitational potential energy sitting on a shelf that is 1.5

m high. 14 Calculate the mass of a person with 750,000 J of gravitational potential energy that has climbed

1000 m above the ground. 15 Calculate the height above the ground of a person with 900,000 J of gravitational potential energy

and a mass of 80 kg. 16 Calculate the amount of elastic potential energy stored by a spring with a spring constant of 20 N/m

extended elastically by 3 cm. 17 A spring has 80 J of stored energy after being extended by 80 cm. Calculate the spring constant. 18 A car has a top speed of 12 m / s and a mass of 800 g. Calculate the maximum kinetic energy of the

car. 19 A rollercoaster rolls from point A to point B, a drop of 35 m. Calculate the speed of the roller coaster

at point B. Gravitational field strength = 9.8 N / kg. Assume that the decrease in potential energy store is equal to the increase in kinetic energy store.

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Kinetic and Potential Energy Stores p168 CGP Knowledge Answers

1 State the type of energy store that will contain energy if an object is moving. Kinetic energy store 2 What does the amount of energy in an object’s kinetic energy store depend on? Its mass and speed 3 State the kinetic energy equation including units. Kinetic energy (J) = ½ × mass (kg) × speed2 (m/s)2 4 What energy store of an object will be increased when it is lifted upwards. Gravitational potential

energy store 5 State the equation, including units, used to calculate the change in the gravitational potential

energy store of an object. Gravitational potential energy (J) = mass (kg) × gravitational field strength (N/kg) × height (m)

6 What is the relationship between the gravitational potential energy (gpe) store and kinetic energy (ke) store of a falling object when there is no air resistance? Energy lost from gpe store = energy gained in ke store

7 What energy store increases when an object is stretched or squashed? Elastic potential energy store 8 State the equation used, including the units, to find the energy in the elastic potential energy store

of an object. Elastic potential energy (J) = ½ × spring constant (N/m) × extension2 (m)2 9 We can only use the equation above when an object’s limit of proportionality is not exceeded.

Practice Answers

10 Calculate the amount of kinetic energy in the kinetic energy stores of the following objects: a A car with a mass of 1000 kg travelling at 10 m/s. ½ × 1000 × 102 = 50,000 J b A ping pong ball with a mass of 50 g travelling at 3 m/s. ½ × 0.05 × 32 = 0.225 J c A runner with a mass of 80 kg running at 2 m/s. ½ × 80 × 22 = 160 J

11 Calculate the mass of a car with a kinetic energy store of 35,000 J travelling at 10 m/s. ½ × mass × 102 = 35,000. Mass = 700 kg

12 Calculate the speed a car with a kinetic energy store of 35,000 J and a mass of 800 kg. ½ × 800 × speed2 = 35,000. Speed = 9.35 m/s

13 Calculate the mass a football with 8 J of gravitational potential energy sitting on a shelf that is 1.5 m high. Mass × 9.8 × 1.5 = 8. Mass = 0.54 kg

14 Calculate the mass of a person with 750,000 J of gravitational potential energy that has climbed 1000 m above the ground. Mass × 9.8 × 1000 = 750,000. Mass = 76.5 kg

15 Calculate the height above the ground of a person with 900,000 J of gravitational potential energy and a mass of 80 kg. 80 × 9.8 × height = 900,000. Height = 1147.96 m

16 Calculate the amount of elastic potential energy stored by a spring with a spring constant of 20 N/m extended elastically by 3 cm. ½ × 20 × 0.032 = 0.009 J

17 A spring has 80 J of stored energy after being extended by 80 cm. Calculate the spring constant. ½ × spring constant 11 0.82 = 80. Spring constant = 250 N/m

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Specific Heat Capacity p169 CGP Knowledge Questions

1 Complete: The specific heat capacity of a substance is the amount of __________ required to raise the __________ of __________ of a substance by __________.

2 Copy out this equation and write the standard units of measurement beneath: Change in thermal energy = mass × specific heat capacity × change in temperature

3 Which non-standard unit of measurement do you need to multiply by 1,000 to convert into J? 4 What is the change in temperature for this question: How much energy is needed to increase the

temperature of 500 g of lead from 20 oC to 45 oC? The specific heat capacity of lead is 128 J/kg oC. 5 Calculate the final temperature of 120 g of water when 24 kJ of thermal energy is added to it. The

initial temperature of the water is 3.5 oC, and the specific heat capacity of water is 4,200 J/kg oC. 6 Aluminium has a specific heat capacity of 900 J/kg oC. If the thermal energy store of a 2 kg lump of

aluminium reduces by 3,600 J, and the final temperature of the aluminium block is 36 oC, what was the initial temperature of the block?

7 What is the independent variable in the specific heat capacity practical? 8 What is the dependent variable in the specific heat capacity practical? 9 What are the control variables in the specific heat capacity practical? 10 In the specific heat capacity practical, why is it important to insulate the block? 11 Which substance has a higher specific heat capacity: 1 kg of a substance that requires 450 J of

thermal energy to raise its temperature by 1 oC or 1 kg of a substance that requires 275 J of thermal energy to raise its temperature by 1 oC?

12 Complete: If a material has a low specific heat capacity, then it requires (more/less) __________ thermal energy to heat up than a material with a high specific heat capacity.

13 How do you calculate the gradient? 14 After having plotted a graph with ‘mass × change in temperature (oC)’ on the x-axis and ‘change in

thermal energy (J)’ on the y-axis, how do you calculate specific heat capacity? 15 After having plotted a graph with ‘change in thermal energy (J)’ on the x-axis and ‘change in

temperature (oC)’ on the y-axis, how do you calculate specific heat capacity? Practice Questions

16 A glass with a specific heat capacity of 792 J/kg oC has a starting temperature of 12 oC. If the glass has a mass of 0.7 kg and the thermal energy store of the glass increases by 777 J, what is the final temperature of the glass?

17 Use the graph below to determine the mean value of the specific heat capacity of water.

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18 Why might the value calculated for the specific heat capacity of water be greater than the accepted value?

19 Use the graph below to determine the mean value of the specific heat capacity of the metal block.

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Specific Heat Capacity p169 CGP Knowledge Questions

1 Complete: The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 kg of a substance by 1 oC.

2 Copy out this equation and write the standard units of measurement beneath: Change in thermal energy = mass × specific heat capacity × change in temperature

(J) (kg) (J/kg oC) (oC) 3 Which non-standard unit of measurement do you need to multiply by 1,000 to convert into J? kJ 4 What is the change in temperature for this question: How much energy is needed to increase the

temperature of 500 g of lead from 20 oC to 45 oC? The specific heat capacity of lead is 128 J/kg oC. 45 – 20 = 25 oC

5 Calculate the final temperature of 120 g of water when 24 kJ of thermal energy is added to it. The initial temperature of the water is 3.5 oC, and the specific heat capacity of water is 4,200 J/kg oC.

6 Aluminium has a specific heat capacity of 900 J/kg oC. If the thermal energy store of a 2 kg lump of

aluminium reduces by 3,600 J, and the final temperature of the aluminium block is 36 oC, what was the initial temperature of the block?

7 What is the independent variable in the specific heat capacity practical? The material of the metal

block (copper, iron or aluminium) 8 What is the dependent variable in the specific heat capacity practical? The temperature of the

metal block every minute for about 10 minutes 9 What are the control variables in the specific heat capacity practical? Mass of the metal block,

power supplied (as long as the potential difference and current remain constant – power = potential difference × current), insulation around the block, temperature of the surroundings

10 In the specific heat capacity practical, why is it important to insulate the block? To reduce dissipation and ensure that most of the thermal energy transferred to the block is used to increase its temperature

11 Which substance has a higher specific heat capacity: 1 kg of a substance that requires 450 J of thermal energy to raise its temperature by 1 oC or 1 kg of a substance that requires 275 J of thermal energy to raise its temperature by 1 oC? 1 kg of a substance that requires 450 J of thermal energy to raise its temperature by 1 oC

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12 Complete: If a material has a low specific heat capacity, then it requires less thermal energy to heat up than a material with a high specific heat capacity.

13 How do you calculate the gradient? Gradient = y2 - y1

x2 - x1 or

rise

run

14 After having plotted a graph with ‘mass × change in temperature (oC)’ on the x-axis and ‘change in thermal energy (J)’ on the y-axis, how do you calculate specific heat capacity? Calculate the gradient

15 After having plotted a graph with ‘change in thermal energy (J)’ on the x-axis and ‘change in

temperature (oC)’ on the y-axis, how do you calculate specific heat capacity? 1

gradient × mass

Practice Answers

18 Why might the value calculated for the specific heat capacity of water be greater than the

accepted value? Some of the energy supplied does not raise the temperature of the water 19

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Power p170 CGP Knowledge Questions

1 What is power? 2 What is the standard unit of measurement for power? 3 Complete: Work refers to the amount of __________ __________ when a force causes a

__________. 4 What is the standard unit of measurement for work? 5 Define ‘energy’. 6 What is the standard unit of measurement for energy? 7 If 10,000 J of work is done when a woman lifts a dumbbell, how much energy is transferred? 8 Explain your answer to question 2. 9 What is the equation that links work done and power? 10 State the equation that links the variables time, power and energy transferred. 11 What is the standard unit of measurement for time? 12 Complete: 1 J/s = 1 ___ 13 How do you convert kJ into the standard unit of measurement for work? 14 How do you convert kW into the standard unit of measurement for power? 15 Complete: A (more/less) __________ powerful machine is one that transfers a lot of energy in a

short space of time. Practice Questions

16 Two cranes lift a 3,000 kg mass 10 m upwards. The yellow crane completes this task in 17 seconds, whereas the blue crane completes this task in 15 seconds. Which crane is more powerful? Why?

17 The Ferrari race car is more powerful than the McLaren race car. How might this be observed? 18 What does it mean for one machine to be more powerful than another? 19 Calculate the work done when a 3.5 kW lawnmower is used for 45 seconds. 20 How long has a timer been on if it has a power rating of 45 W and has transferred 750 J of energy?

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Power p170 CGP Knowledge Answers

1 What is power? The rate at which energy is transferred or the rate at which work is done 2 What is the standard unit of measurement for power? Watts (W) 3 Complete: Work refers to the amount of energy transferred when a force causes a movement. 4 What is the standard unit of measurement for work? Joules 5 Define ‘energy’. The ability to do work 6 What is the standard unit of measurement for energy? Joules 7 If 10,000 J of work is done when a woman lifts a dumbbell, how much energy is transferred? 10,000

J 8 Explain your answer to question 2. Work done is equivalent to energy transferred

9 What is the equation that links work done and power? Power = work done

time

10 State the equation that links the variables time, power and energy transferred. Power = energy transferred

time

11 What is the standard unit of measurement for time? Seconds (s) 12 Complete: 1 J/s = 1 W 13 How do you convert kJ into the standard unit of measurement for work? Multiply by 1,000 14 How do you convert kW into the standard unit of measurement for power? Multiply by 1,000 15 Complete: A (more/less) more powerful machine is one that transfers a lot of energy in a short

space of time. Practice Answers

16 Two cranes lift a 3,000 kg mass 10 m upwards. The yellow crane completes this task in 17 seconds, whereas the blue crane completes this task in 15 seconds. Which crane is more powerful? Why? The blue crane is more powerful because it transfers energy in a shorter space of time

17 The Ferrari race car is more powerful than the McLaren race car. How might this be observed? The Ferrari might complete a race course in a shorter space of time compared to the McLaren

18 What does it mean for one machine to be more powerful than another? A more powerful machine transfers energy in a shorter space of time

19 Calculate the work done when a 3.5 kW lawnmower is used for 45 seconds.

20 How long has a timer been on if it has a power rating of 45 W and has transferred 750 J of energy?

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Reducing Unwanted Energy Transfers p171 CGP Knowledge Questions

1 What does the Law of Conservation of Energy state? 2 When there are energy transfers in a closed system, what happens to the total energy of the

system? 3 What happens to the internal energy of the particles that form the surroundings every time work is

done? 4 What is another way for saying that energy is given out to the surroundings? 5 Give an example of a wasted energy transfer. 6 What can lubrication and the use of thermal insulation reduce? 7 Explain how energy transfers across a material during conduction? 8 What additional explanation is needed to explain conduction in a metal? 9 Complete: The lower the thermal conductivity of a material, (faster/slower) __________ energy

transfers through the material. 10 What word describes materials with: a) high thermal conductivity; b) low thermal conductivity? 11 Which material has the highest thermal conductivity out of iron, glass and rubber? 12 Complete: The __________ the walls, the lower their thermal conductivity. 13 State two ways by which energy losses in buildings can be reduced. 14 State the four types of thermal insulation used in buildings.

Practice Questions

15 Whilst the net change in energy for a closed system composed of a hot cup of tea and a cold metal spoon will be zero, state an energy transfer that occurs.

16 An engine has moving parts. The frictional forces acting against moving parts in the engine is causing some energy in the system to be dissipated. How can these frictional forces be reduced, so reducing unwanted energy transfers?

17 The diagram on the right shows how much heat is lost each second from different parts of an uninsulated house. Each year, the house costs £760 to heat. How much money is being wasted because of heat lost through the roof?

18 What happens to the wasted energy? 19 The drawing shows parts of a house

where it is possible to reduce the amount of energy lost. Give one way in which the amount of energy lost can be reduced from each of the following parts of the house:

a 1, 2 and 4 b 5 c 7

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Reducing Unwanted Energy Transfers p171 CGP Knowledge Answers

1 What does the Law of Conservation of Energy state? Energy cannot be created or destroyed, it can only be transferred usefully, stored or dissipated

2 When there are energy transfers in a closed system, what happens to the total energy of the system? Nothing: the total energy remains the same

3 What happens to the internal energy of the particles that form the surroundings every time work is done? The internal energy of the particles that form the surroundings increases

4 What is another way for saying that energy is given out to the surroundings? Dissipation / wasted 5 Give an example of a wasted energy transfer. The thermal energy store of the surroundings

increasing 6 What can lubrication and the use of thermal insulation reduce? Unwanted energy transfers 7 How does energy transfer across a material during conduction?

Heating causes the particles that form the material to vibrate more

Particles collide with neighbouring particles each other

Causing extra kinetic energy to be transferred 8 What additional explanation is needed to explain conduction in a metal?

Metals have delocalised electrons

Which are free to move throughout the structure

These delocalised electrons gain and transfer extra energy throughout the metal. 9 Complete: The lower the thermal conductivity of a material, (faster/slower) slower energy transfers

through the material. 10 What word describes materials with: a) high thermal conductivity; b) low thermal conductivity?

a) thermal conductor; b) thermal insulator 11 Which material has the highest thermal conductivity out of iron, glass and rubber? Iron 12 Complete: In a building, the thicker the walls, the lower their thermal conductivity. 13 State two ways by which energy losses in buildings can be reduced. Thicker walls made of a material

with low thermal conductivity and thermal insulation. 14 State the four types of thermal insulation used in buildings. Cavity wall insulation, loft insulation,

double-glazing, draught excluders Practice Answers

15 Whilst the net change in energy for a closed system composed of a hot cup of tea and a cold metal spoon will be zero, state an energy transfer that occurs. Energy transfers from the thermal energy store of the tea to the (useless) thermal energy store of the metal spoon due to heating

16 An engine has moving parts. The frictional forces acting against moving parts in the engine is causing some energy in the system to be dissipated. How can these frictional forces be reduced, so reducing unwanted energy transfers? Use lubrication, such as oil, on the engine’s moving parts

17 The diagram on the right shows how much heat is lost each second from different parts of an uninsulated house. Each year, the house costs £760 to heat. How much money is being wasted because of heat lost through the roof? 150 + 200 + 66 + 75 + 109 = 600 J 150 ÷ 600 = 0.25

760 × 0.25 = £190 (3 s.f.)

18 What happens to the wasted energy? Dissipated or transferred to surroundings/atmosphere or becomes spread out

19 The drawing shows parts of a house where it is possible to reduce the amount of energy lost. Give one way in which the amount of energy lost can be reduced from each of the following parts of the house:

a 1, 2 and 4 insulation b 5 double glazing c 7 draught excluder

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Efficiency p172 CGP Knowledge Questions

1 Complete: A more __________ energy transfer is one that transfers more of the input energy usefully.

2 What is the equation for efficiency of an energy transfer? 3 What is the equation for efficiency of a power output? 4 What is the standard unit of measurement for efficiency? 5 How do you convert % into the standard unit of measurement for efficiency? 6 True or false? No device is 100% efficient. 7 BUG the exam question below, boxing the unknown value and underlining the known values. Write

‘total input’, ‘useful output’ or ‘efficiency’ next to each value. a When 200 J is transferred to the solar cells, 50 J is transferred to the chemical energy

store of the batteries, 50 J to the surroundings as sound waves and 100 J to the thermal energy store of the surroundings. Calculate the efficiency of the solar cells.

b On average, British Light solar cells with an efficiency of 0.15 transfer 0.6 J of energy as light waves each second. Calculate the average energy input each second to the device.

Practice Questions

8 Which light bulb is more efficient: a A 30 W light bulb that uses 600 J of energy in a certain period of time. In that time, it

transfers 450 J of energy into the surroundings as light waves. b A 15 W light bulb that uses 80 J of energy in a certain period of time. In that time, it transfers

50 J of energy into the surroundings as light waves. 9 A light bulb receives 300 J of energy electrically. 180 J of this energy is transferred by light waves to

the surroundings while the remaining 120 J is transferred into the thermal energy store of the surroundings. Calculate the efficiency and the percentage efficiency of this light bulb.

10 1,200 J of useful energy help to power a dishwasher that is 78 % efficient. What is the total energy transfer?

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Efficiency p172 CGP Knowledge Answers

1 Complete: A more efficient energy transfer is one that transfers more of the input energy usefully.

2 What is the equation for efficiency of an energy transfer? Efficiency = useful output energy transfer

total input energy transfer

3 What is the equation for efficiency of a power output? Efficiency = useful power output

total power input

4 What is the standard unit of measurement for efficiency? There is no unit of measurement for efficiency

5 How do you convert % into the standard unit of measurement for efficiency? Divide by 100 6 True or false? No device is 100% efficient. True 7 BUG the exam question below, boxing the unknown value and underlining the known values. Write

‘total input’, ‘useful output’ or ‘efficiency’ next to each value. total input useful output

a When 200 J is transferred to the solar cells, 50 J is transferred to the chemical energy store of the batteries, 50 J to the surroundings as sound waves and 100 J to the thermal energy store of the surroundings.

efficiency

Calculate the efficiency of the solar cells. efficiency useful output

b On average, British Light solar cells with an efficiency of 0.15 transfer 0.6 J of energy as light waves each second.

total input

Calculate the average energy input each second to the device.

Practice Answers

8 Which light bulb is more efficient: The 30 W light bulb (see working out below) a A 30 W light bulb that uses 600 J of energy in a certain period of time. In that time, it

transfers 450 J of energy into the surroundings as light waves. 450 ÷ 600 = 0.75 b A 15 W light bulb that uses 80 J of energy in a certain period of time. In that time, it transfers

50 J of energy into the surroundings as light waves. 50 ÷ 80 = 0.625 9 A light bulb receives 300 J of energy electrically. 180 J of this energy is transferred by light waves to

the surroundings while the remaining 120 J is transferred into the thermal energy store of the surroundings. Calculate the efficiency and the percentage efficiency of this light bulb.

10 1,200 J of useful energy help to power a dishwasher that is 78 % efficient. What is the total energy

transfer?

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Energy Resources 1 p173-174 CGP

Knowledge Questions 1 What does ‘non-renewable energy resource’ mean? 2 Identify non-renewable energy resources. 3 What name is given to energy resources that can be replenished as it is used? 4 There are seven types of energy resources that never run out. State as many as you possibly can –

three are linked to water. 5 Which energy resource formed underground over millions of years from the remains of organisms? 6 State three uses of energy resources. 7 What uses does wind energy have?

a Why isn’t wind energy reliable? b What impact do wind turbines have on the environment? c Are there any other disadvantages? d Complete: Advantages include no __________ costs and low __________ costs.

8 Which energy resource generates electric currents directly from sunlight? a Complete: Solar cells are used to generate electricity on a __________ scale, often to power

__________ __________ in remote places and artificial __________. b Why are solar water heaters used? c Is this energy resource reliable? d Does the energy resource cause any pollution? e Are there any disadvantages?

9 Which energy resource is found in underground thermal energy stores? a What are the uses of this energy resource? b Is this energy resource reliable? c Does this energy resource have negative environmental impacts?

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Energy Resources 1 p173-174 CGP Knowledge Answers

1 What does ‘non-renewable energy resource’ mean? It will run out one day 2 Identify non-renewable energy resources. Fossil fuels and nuclear fuel 3 What name is given to energy resources that can be replenished as it is used? Renewable energy

resources 4 There are seven types of energy resources that never run out. State as many as you possibly can –

three are linked to water. Solar, wind, geothermal, biofuel, hydro-electricity, tides, water waves 5 Which energy resource formed underground over millions of years from the remains of organisms?

Fossil fuels 6 State three uses of energy resources. Transport, generating electricity and heating 7 What uses does wind energy have? Generating electricity

a Why isn’t wind energy reliable? Wind turbines stop when the wind stops or is too strong. b What impact do wind turbines have on the environment? Spoil the view and can be very

noisy. c Are there any other disadvantages? Initial cost of wind turbines are high d Complete: Advantages include no fuel costs and low running costs.

8 Which energy resource generates electric currents directly from sunlight? Solar energy a Complete: Solar cells are used to generate electricity on a small scale, often to power road

signs in remote places and artificial satellites. b Why are solar water heaters used? To heat water c Is this energy resource reliable? No, only in the daytime d Does the energy resource cause any pollution? No e Are there any disadvantages? Initial cost of solar cells or solar water heaters is expensive

9 Which energy resource is found in underground thermal energy stores? Geothermal energy a What are the uses of this energy resource? Generating electricity and heating b Is this energy resource reliable? Yes c Does this energy resource have negative environmental impacts? No. However, there

aren’t many suitable locations for geothermal power plants.

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Energy Resources 2 p175-177 CGP

Knowledge Questions 1 Which energy resource generates electricity from falling water?

a How is this energy resource used? b Is this energy resource reliable? c Complete: Dams can cause __________ of the valley (rotting vegetation releases methane

and CO2) and possible loss of __________. Reservoirs can look __________, too. d Complete: An advantage is that this energy resource can provide an __________ response

to an increased demand for electricity. 2 How is energy from wave power used?

a How damaging is this energy resource on the environment? There are lots of disadvantages, so why might wave power ever be used? Complete: After the high initial costs, there are no __________ costs and low __________ costs. Wave power can be very useful on __________ __________.

3 For which energy resource are big dams build across river estuaries (where the mouth of the river meets the sea)?

a How is the energy harvested from this energy resource used? b How reliable is this energy resource? c How damaging is this energy resource on the environment? d Complete: Despite the environmental concerns, this energy resource has the potential to

generate __________ energy. 4 Which energy resource is made from plant products or animal dung?

a How is the energy harvested from this energy resource used? b Complete: This energy resource __________ respond to immediate energy demands. To

combat this, __________ are continuously produced and stored for when they are __________.

c How damaging is this energy resource on the environment?

5 Which energy resource are coal, oil and natural gas examples of? a How is the energy harvested from this energy resource used? b How reliable is this energy resource? c How damaging is this energy resource on the environment? d Are there any other disadvantages?

6 Which energy resource relies on a supply of uranium or plutonium? a How is the energy harvested from this energy resource used? b How reliable is this energy resource? c How damaging is this energy resource on the environment? d Are there any other disadvantages?

7 Why are some energy resources more reliable than others? 8 Which energy resources are the most reliable? 9 Was electricity use higher in the 20th or 21st century? 10 What are the two main reasons that people want to use more renewable energy resources? 11 Complete: Despite the evidence, scientists don’t have the __________ to make people, companies

or governments change their __________ with regards to __________ energy resources.

20

Energy Resources 2 p175-177 CGP

Knowledge Answers 1 Which energy resource generates electricity from falling water? Hydro-electric energy

a How is this energy resource used? To generate electricity b Is this energy resource reliable? Yes, except in times of drought c Complete: Dams can cause flooding of the valley (rotting vegetation releases methane and

CO2) and possible loss of habitat. Reservoirs can look ugly, too. d Complete: An advantage is that this energy resource can provide an immediate response

to an increased demand for electricity. 2 How is energy from wave power used? To generate electricity

a How damaging is this energy resource on the environment? Disturbing the sea bed and the habitats of marine animals, spoiling the view and being a hazard to boats

b There are lots of disadvantages, so why might wave power ever be used? Complete: After the high initial costs, there are no fuel costs and low running costs. Wave power can be very useful on small islands.

3 For which energy resource are big dams build across river estuaries (where the mouth of the river meets the sea)? Tidal energy

a How is the energy harvested from this energy resource used? To generate electricity b How reliable is this energy resource? Pretty reliable as tides happen twice a day, but a

lower tide will provide significantly less energy c How damaging is this energy resource on the environment? Tidal barrages prevent free

access by boats, spoil the view and change the habitat of the wildlife d Complete: Despite the environmental concerns, this energy resource has the potential to

generate a lot of energy. 4 Which energy resource is made from plant products or animal dung? Biofuels

a How is the energy harvested from this energy resource used? To generate electricity or for transport

b Complete: This energy resource cannot respond to immediate energy demands. To combat this, biofuels are continuously produced and stored for when they are needed.

c How damaging is this energy resource on the environment? Whilst biofuels are carbon neutral (the plants take in as much carbon dioxide when they grow as they give out when they burn), large areas of forest have been cleared to grow biofuels, resulting in a loss of habitat for many species.

5 Which energy resource are coal, oil and natural gas examples of? Fossil fuels a How is the energy harvested from this energy resource used? Transport, generating

electricity and heating b How reliable is this energy resource? Very, as it can provide base-load electricity and can

respond quickly to changes in demand c How damaging is this energy resource on the environment? Very, they release CO2 when

burned, adding to the greenhouse effect and contributing to global warming. Burning coal and oil releases sulfur dioxide, which causes acid rain.

d Are there any other disadvantages? Commissioning and decommissioning power stations is very expensive

6 Which energy resource relies on a supply of uranium or plutonium? Nuclear energy a How is the energy harvested from this energy resource used? To generate electricity b How reliable is this energy resource? Very c How damaging is this energy resource on the environment? No carbon dioxide or sulfur

dioxide is released but the nuclear waste is very dangerous and difficult to dispose of. d Are there any other disadvantages? Commissioning and decommissioning power stations

is very expensive 7 Why are some energy resources more reliable than others? Some rely on the weather (solar, wind),

which may not be favourable, but some are always accessible. 8 Which energy resources are the most reliable? Fossil fuels and nuclear energy 9 Was electricity use higher in the 20th or 21st century? 20th century

21

10 What are the two main reasons that people want to use more renewable energy resources? They now know of the damaging effect non-renewable energy resources can have on the environment and because, one day, non-renewable energy resources will run out

11 Complete: Despite the evidence, scientists don’t have the power to make people, companies or governments change their behaviour with regards to non-renewable energy resources.

22

23

Current and Circuit Symbols p179 CGP

Knowledge Questions 1 Complete: Current is the ___A___ of electrical ___B___. 2 How is ‘size of current’ defined? 3 What three things are needed for current to flow? 4 What is the standard unit of measurement for current? 5 What is the ‘amount of energy transferred per coulomb of charge’? 6 What is the standard unit of measurement for your answer to question 4? 7 What is the scientific symbol for: Current? Potential difference? Resistance? Charge? 8 What is resistance? 9 What are the standard unit of measurement for resistance? 10 Complete: Resistance is __________ __________ to current. 11 Complete: Resistance is __________ __________ to potential difference. 12 State the formula which links time, current and charge. 13 What is the standard unit of measurement for charge? 14 Draw and label what each of the circuit symbols represent.

Practice Questions

15 Complete: If a circuit has high resistance, the current will be… 16 Complete: If a component has high potential difference, the resistance of the component must

be… 17 Which circuit has the higher current? Explain why.

18 A 2 A current flows through a lamp in 10 seconds. How many Coulombs pass through the lamp? 19 Calculate current in a light bulb if 30 C of charge flows through it every 15 s. 20 Calculate how long it would take a current of 3500 mA to deliver 700 C.

A

B

C

D

E

F

G

H

I

J

K

L

M

N

24

Current and Circuit Symbols p179 CGP

Knowledge Answers 1 Complete: Current is the flow of electrical charge. 2 How is ‘size of current’ defined? Rate of flow of electrical charge. 3 What three things are needed for current to flow? Source of potential difference (power supply),

closed circuit (no breaks), all components made of electrical conductors. 4 What is the standard unit of measurement for current? Amps (A) 5 What is the ‘amount of energy transferred per coulomb of charge’? Potential difference (V) 6 What is the standard unit of measurement for your answer to question 4? Volts (V) 7 What is the scientific symbol for: Current? I Potential difference? V Resistance? R Charge? Q 8 What is resistance? Opposition to current / opposition to the flow of charge 9 What are the standard unit of measurement for resistance? Ohms (Ω) 10 Complete: Resistance is inversely proportional to current. 11 Complete: Resistance is directly proportional to potential difference. 12 State the formula which links time, current and charge. Q = I x t OR I = Q/t 13 What is the standard unit of measurement for charge? Coulombs (C) 14 State what each of the circuit symbols represent.

Practice Answers

15 Complete: If a circuit has high resistance, the current will be low. 16 Complete: If a component has high potential difference, the resistance of the component must be high. 17 Which circuit has the higher current? Explain why. A. Resistance is lower so current is higher. 18 A 2 A current flows through a lamp in 10 seconds. How many Coulombs pass through the lamp?

19 Calculate current in a light bulb if 30 C of charge flows through it every 15 s.

20 Calculate how long it would take a current of 3500 mA to deliver 700 C.

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Resistance and V = IR p180 CGP Knowledge Questions

1 State the formula linking potential difference, current and resistance including the units. 2 Name the piece of equipment used to measure current and state how it must be connected in a

circuit. 3 Name the piece of equipment used to measure potential difference and state how it must be

connected in a circuit. 4 Draw a circuit diagram of the circuit used to investigate how the length of a wire affects its

resistance. 5 Describe how the length of the wire in the circuit is changed. 6 Why is it important to turn off the current between taking readings? 7 What is the relationship between resistance and the length of a wire? 8 What does a graph of resistance against the length of a wire look like?

Practice Questions

9 Calculate the current flowing through a lamp with resistance of 2.5 Ω and 12.5 V of potential difference across it.

10 Calculate the potential difference through a wire with 16 Ω of resistance and 400 mA flowing through it.

11 A microwave oven has a potential difference measured across it of 120,000 mV. 0.8 A of current flow through it. Calculate the resistance of the microwave oven.

12 A Tesla car is charging. Its battery receives 240 V at 70 A. What is the resistance in the battery?

26

Resistance and V = IR p180 CGP Knowledge Answers

1 State the formula linking potential difference, current and resistance including the units. Potential difference (V) = current (A) × resistance (Ω)

2 Name the piece of equipment used to measure current and state how it must be connected in a circuit. Ammeter, connected in series

3 Name the piece of equipment used to measure potential difference and state how it must be connected in a circuit. Voltmeter, connected in parallel with the component you want to measure the potential difference across

4 Draw a circuit diagram of the circuit used to investigate how the length of a wire affects its resistance.

5 Describe how the length of the wire in the circuit is changed. Connect one crocodile clip to one end of the wire and another 10 cm away. Move the second crocodile clip along to change the length of the wire.

6 Why is it important to turn off the current between taking readings? The wire may heat up if the current is left on and this will affect its resistance.

7 What is the relationship between resistance and the length of a wire? They are directly proportional.

8 What does a graph of resistance against the length of a wire look like? A straight line through the origin.

Practice Answers 9 Calculate the current flowing through a lamp with resistance of 2.5 Ω and 12.5 V of potential

difference across it. 12.5/2.5 = 5 A 10 Calculate the potential difference through a wire with 16 Ω of resistance and 400 mA flowing

through it. 16 x 0.4 = 6.4 V 11 A microwave oven has a potential difference measured across it of 120,000 mV. 0.8 A of current

flow through it. Calculate the resistance of the microwave oven. 120/0.8 = 150 Ω 12 A Tesla car is charging. Its battery receives 240 V at 70 A. What is the resistance in the battery?

240/70 = 3.4 Ω

27

Resistance and I-V Characteristics p181 CGP Knowledge Questions

1 What happens to resistance of an Ohmic conductor when current flowing through it changes? 2 Give two examples of Ohmic conductors. 3 The resistance of which conductor changes when current changes? 4 State examples of the abovementioned conductor. 5 Describe the relationship between the current and potential difference across an Ohmic conductor,

at a constant temperature. 6 On an IV characteristic graph, what is plotted on the x- and y- axis? 7 Sketch an IV characteristic graph for a(n):

Ohmic conductor

Diode

Wire

Filament lamp

Resistor 8 Draw a circuit that is used to investigate the IV characteristic of a component such as a filament

lamp. 9 Explain the role of the variable resistor in the circuit used to investigate the IV characteristic of a

component. 10 Instead of using a variable resistor, what other way can you change the potential difference of the

component being investigated?

Practice Questions 11 How can you tell from looking at an IV characteristic graph whether a conductor is Ohmic or non-

Ohmic? 12 Describe how a student would use the circuit on the right to take the readings necessary to

determine the resistance of the resistor R.

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Graph 1 Graph 2 Graph 3

Resistance and I-V Characteristics p181 CGP Knowledge Answers

1 What happens to resistance of an Ohmic conductor when current flowing through it changes? Resistance stays the same

2 Give two examples of Ohmic conductors. Wire, resistor 3 The resistance of which conductor changes when current changes? Non-ohmic conductor 4 State examples of the abovementioned conductor. Filament lamp, diode 5 Describe the relationship between the current and potential difference across an Ohmic conductor,

at a constant temperature. At a constant temperature, the current flowing through an Ohmic conductor is directly proportional to the potential difference across it.

6 On an IV characteristic graph, what is plotted on the x- and y- axis? Current on the y-axis and potential difference on the x-axis.

7 Sketch an IV characteristic graph for a(n):

Ohmic conductor Graph 1

Diode Graph 3

Wire Graph 1

Filament lamp Graph 2

Resistor Graph 1

8 Draw a circuit that is used to investigate the IV characteristic of a component such as a filament lamp. See circuit diagram on the right.

9 Explain the role of the variable resistor in the circuit used to investigate the IV characteristic of a component. It changes the potential difference

10 Instead of using a variable resistor, what other way can you change the potential difference of the component being investigated? Changing the number of cells in the battery (or the voltage of the power pack) changes the potential difference across the component being investigated.

Practice Answers

11 How can you tell from looking at an IV characteristic graph whether a conductor is Ohmic or non-Ohmic? If the graph shows a straight line going through the origin (directly proportional relationship), the conductor is Ohmic; if not, it’s a non-Ohmic conductor.

12 Describe how a student would use the circuit on the right to take the readings necessary to determine the resistance of the resistor R.

Switch on circuit

Read both ammeter and voltmeter

Adjust the variable resistor

Take further readings

Draw a graph of I against V

Find the inverse of the gradient

29

Circuit Devices p182 CGP Knowledge Questions

1 Draw the circuit symbol for an LDR. 2 Draw the circuit symbol for a thermistor. 3 What is the resistance of an LDR dependent on? 4 What is the resistance of a thermistor dependent on? 5 What happens to the resistance of a thermistor when its temperature increases? 6 What happens to the resistance of an LDR when light intensity decreases? 7 What happens to the resistance of an LDR when light intensity increases? 8 Give an example of an application of an LDR. 9 Give an example of an application of a thermistor.

Practice Questions

10 For the circuit below: a What is the total potential difference across the resistor and the thermistor? b What will happen to the resistance of the thermistor if the temperature decreases? c What then happens to the potential difference across the thermistor? d What happens to the potential difference across the resistor?

11 For the circuit below:

a What will happen to the resistance of the LDR when light intensity increases? b What will then happen to the potential difference across the LDR? c What will happen to the potential difference across the resistor?

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Circuit Devices p182 CGP Knowledge Answers

1 Draw the circuit symbol for an LDR.

2 Draw the circuit symbol for a thermistor. 3 What is the resistance of an LDR dependent on? Light intensity 4 What is the resistance of a thermistor dependent on? Temperature 5 What happens to the resistance of a thermistor when its temperature increases? Resistance

decreases. 6 What happens to the resistance of an LDR when light intensity decreases? Resistance stays the

same 7 What happens to the resistance of an LDR when light intensity increases? Resistance decreases 8 Give an example of an application of an LDR. Automatic night lights, outdoor lighting, burglar

detectors. 9 Give an example of an application of a thermistor. Car engine temperature sensor, electronic

thermostats.

Practice Answers 10 For the circuit below:

a What is the total potential difference across the resistor and the thermistor? 12 V b What will happen to the resistance of the thermistor if the temperature decreases?

Resistance increases c What then happens to the potential difference across the thermistor? PD increases d What happens to the potential difference across the resistor? Potential difference

decreases

11 For the circuit below:

a What will happen to the resistance of the LDR when light intensity increases? Resistance decreases

b What will then happen to the potential difference across the LDR? PD across LDR decreases c What will happen to the potential difference across the resistor? PD across resistor

increases

31

Series and Parallel Circuits p183-184 CGP Knowledge Questions

1 How are the different components connected in a series circuit? 2 What happens in a series circuit if a component is removed or disconnected or there is a break in

the circuit? 3 What happens to the potential difference from the power supply in a series circuit? 4 What is true about the current in a series circuit? 5 How do you find the total resistance of all of the components in a series circuit? 6 How do you find the total potential difference of cells connected in series with each other? 7 If one component in a parallel circuit breaks, will the other components still work? 8 What is true about the potential difference in a parallel circuit? 9 What happens to the current in a parallel circuit? 10 What happens to the total resistance of a parallel circuit if another resistor is added in parallel?

Practice Questions

11 A cell, a resistor, a lamp and an ammeter are connected in series.

Complete the following sentences using the words greater than, less than and the same as. Current through the battery is __________ the current through the ammeter. Potential difference across the battery is __________ the potential difference across the resistor. Current through the lamp is __________ the current through the resistor. Potential difference across the lamp is __________ the potential difference across the battery.

12 The cell in the circuit above has a potential difference of 3.0 V and the resistor has a resistance of .1.0 Ω. The ammeter reading is 0.2 A.

a Calculate the potential difference across the resistor. b Calculate the potential difference across the lamp.

13 The ammeter reading for the circuit below is 0.36 A. Calculate the potential difference across: the 10 Ω resistor, the 15 Ω resistor, the battery.

14 Calculate the following quantities for the circuit below:

a The potential difference, V1, across the filament lamp with a resistance of 3 Ω. b The potential difference, V2, across the filament lamp with an unknown resistance. c The current flowing through the filament lamp with a resistance of 3 Ω. d The resistance of the resistor with a potential difference of 4 V across it. e The resistance of the filament lamp with the unknown resistance. f The total current in the circuit, A1.

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Series and Parallel Circuits p183-184 CGP Knowledge Answers

1 How are the different components connected in a series circuit? One after another/in a line, end to end.

2 What happens in a series circuit if a component is removed or disconnected or there is a break in the circuit? Current will not flow and all the components stop working.

3 What happens to the potential difference from the power supply in a series circuit? The potential difference is shared between the different components.

4 What is true about the current in a series circuit? The current the same everywhere/in every component.

5 How do you find the total resistance of all of the components in a series circuit? Add the individual resistances together.

6 How do you find the total potential difference of cells connected in series with each other? Add the individual potential differences together.

7 If one component in a parallel circuit breaks, will the other components still work? Yes 8 What is true about the potential difference in a parallel circuit? The potential difference is the same

across all components. 9 What happens to the current in a parallel circuit? The total current is shared among the different

branches. 10 What happens to the total resistance of a parallel circuit if another resistor is added in parallel? The

total resistance will decrease.

Practice Answers 11 A cell, a resistor, a lamp and an ammeter are connected in series.

Complete the following sentences using the words greater than, less than and the same as. Current through the battery is the same as the current through the ammeter. Potential difference across the battery is greater than the potential difference across the resistor. Current through the lamp is the same as the current through the resistor. Potential difference across the lamp is less than the potential difference across the battery.

12 The cell in the circuit above has a potential difference of 3.0 V and the resistor has a resistance of 1.0 Ω. The ammeter reading is 0.2 A.

a Calculate the potential difference across the resistor. 1.1 × 0.2 = 0.22 V b Calculate the potential difference across the lamp. 3 - 0.22 = 2.7 V

13 The ammeter reading for the circuit below is 0.36 A. Calculate the potential difference across:

the 10 Ω resistor. 10 × 0.36 = 3.6 V

the 15 Ω resistor. 15 × 0.36 = 5.4 V

the battery. 5.4 + 3.6 = 9 V 14 Calculate the following quantities for the circuit above:

a The potential difference, V1, across the filament lamp with a resistance of 3 Ω. 9 V b The potential difference, V2, across the filament lamp with an unknown resistance. 9 - 4 =

5 V c The current flowing through the filament lamp with a resistance of 3 Ω. 9/3 = 3 A d The resistance of the resistor with a potential difference of 4 V across it. 4/2 = 2 Ω e The resistance of the filament lamp with the unknown resistance. 5/2 – 2.5 Ω f The total current in the circuit, A1. 3 + 2 = 5 A

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Investigating Resistance p185 CGP Knowledge Questions

1 State the formula linking potential difference, current and resistance including the units. 2 Name the piece of equipment used to measure current and state how it must be connected in a

circuit. 3 Draw a circuit with a battery, an ammeter and two resistors in series. 4 Draw a circuit with a battery, an ammeter and two resistors in parallel. 5 Sketch a graph showing how the number of resistors in a circuit changes the total resistance for a

series circuit. 6 Sketch a graph showing how the number of resistors in a circuit changes the total resistance for a

parallel circuit. 7 Describe how you would investigate the effect on the resistance in a circuit of adding resistors in

series. 8 Describe how you would investigate the effect on the resistance in a circuit of adding resistors in

parallel. 9 What happens to the total resistance of a circuit when more resistors are added in series? 10 What happens to the total resistance of a circuit when more resistors are added in parallel?

34

Investigating Resistance p185 CGP Knowledge Answers

1 State the formula linking potential difference, current and resistance including the units. Potential difference (V) = current (A) × resistance (Ω)

2 Name the piece of equipment used to measure current and state how it must be connected in a circuit. Ammeter, connected in series

3 Draw a circuit with a cell, an ammeter and two resistors in series.

4 Draw a circuit with a battery, an ammeter and two resistors in parallel. 5 Sketch a graph showing how the number of resistors in a circuit changes the total resistance for a

series circuit. (below)

6 Sketch a graph showing how the number of resistors in a circuit changes the total resistance for a

parallel circuit. (above left) 7 Describe how you would investigate the effect on the resistance in a circuit of adding resistors in

series.

Build a circuit with a battery, one resistor and an ammeter.

Note down the potential difference of the battery and read the current from the ammeter.

Calculate the resistance using the equation V = I x R

Now add another resistor in series with the first one.

Read the new current from the ammeter and calculate the total resistance using V = I x R

Repeat this again with 3 and 4 resistors in series. 8 Describe how you would investigate the effect on the resistance in a circuit of adding resistors in

parallel.

Build a circuit with a battery, one resistor and an ammeter.

Note down the potential difference of the battery and read the current from the ammeter.

Calculate the resistance using the equation V = I x R

Now add another resistor in parallel with the first one.

Make sure to place the ammeter so that you are measuring the total current in the circuit.

Calculate the total resistance using V = I x R

Repeat the steps again for 3 and 4 resistors in parallel. 9 What happens to the total resistance of a circuit when more resistors are added in series? Total

resistance increases 10 What happens to the total resistance of a circuit when more resistors are added in parallel? Total

resistance decreases

35

Electricity in the Home p186 CGP

Knowledge Questions

1 Describe what is meant by an alternating current (ac) supply. 2 Describe what is meant by a direct current (dc) supply. 3 What type of current is the UK mains supply? 4 What is the potential difference and frequency of the UK mains supply? 5 What type of current do cells and batteries supply? 6 Complete the following table about the different wires you find in electrical appliances:

Name of wire Colour of insulation Function

Live

Neutral

Earth

7 What would happen to a person who touches the live wire? 8 What potential difference is our body at?

Practice Questions

9 Name the following: a Green and yellow wire b Blue wire c Brown wire

36

Electricity in the Home p186 CGP Knowledge Answers

1 Describe what is meant by an alternating current (ac) supply. An electricity supply where the current is constantly changing direction.

2 Describe what is meant by a direct current (dc) supply. An electricity supply where the current always flows in the same direction.

3 What type of current is the UK mains supply? Alternating current 4 What is the potential difference and frequency of the UK mains supply? 230 V and 50 Hz 5 What type of current do cells and batteries supply? Direct current 6 Complete the following table about the different wires you find in electrical appliances:

Name of wire Colour of insulation Function

Live Brown Provides the alternating potential difference from the mains supply and is at 230 V

Neutral Blue Completes the circuit and carries away current and is at 0 V

Earth Yellow and green Stops the appliance casing from becoming live if a fault develops and the live wire touches the casing

7 What would happen to a person who touches the live wire? A large potential difference would be produced across the person’s body and a current would flow through them. This is an electric shock and could injure or kill the person.

8 What potential difference is our body at? 0 V Practice Answers

9 Name the following: a Green and yellow wire – Earth b Blue wire – Neutral c Brown wire – Live

37

Electrical Power p187-188 CGP Knowledge Questions

1 What does the total energy transferred by an appliance depend on? 2 State the equation, including the units, linking energy, power and time. 3 What is meant by the power rating of an appliance? 4 Why is a higher power appliance not necessarily better than a low power appliance? 5 What happens when an electrical charge goes through a potential difference? 6 When a charge goes through a power supply what happens? 7 What happens when a charge goes through a circuit component? 8 State the formula, including the units, that links energy transferred, charge and potential difference. 9 State the equation, including the unit that links power, potential difference and current. 10 State the equation, including the units, that links power, current and resistance.

Practice Questions

11 Calculate the power supplied to a motor with 7 A of current flowing through it and 2.5 V of potential difference across it.

12 Calculate the potential difference across a lamp with 0.5 A of current flowing through it and 12 W of power supplied to it.

13 Calculate the current flowing through a lamp with a 95 W power rating and a resistance of 150 Ω. 14 A printer is supplied with 50 W of power. The current flowing through the printer is measured at

0.25 A. Calculate the potential difference. 15 Calculate the voltage of a battery which supplies 12 J to 6 C. 16 Calculate the amount of energy delivered by a 4V cell to 8 C. 17 A vacuum cleaner motor is supplied with 2 kW of power and 12 A of current flows. Calculate the

resistance of the motor.

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Electrical Power p187-188 CGP Knowledge Answers

1 What does the total energy transferred by an appliance depend on? How long it is on for and its power rating

2 State the equation, including the units, linking energy, power and time. Energy transferred (J) = power (W) × time (s)

3 What is meant by the power rating of an appliance? The maximum power they can operate at which is safe

4 Why is a higher power appliance not necessarily better than a low power appliance? The high-power appliance might be less efficient than the low power appliance meaning it transfers less energy usefully.

5 What happens when an electrical charge goes through a potential difference? Energy is transferred 6 When a charge goes through a power supply what happens? The charge is supplied with energy 7 What happens when a charge goes through a circuit component? The charge gives up or transfers

energy to the component 8 State the formula, including the units, that links energy transferred, charge and potential difference.

Energy transferred (J) = charge (C) × potential difference (V) 9 State the equation, including the unit, that links power, potential difference and current. Power (W)

= potential difference (V) × current (A) 10 State the equation, including the units, that links power, current and resistance. Power (W) =

current2 (A) × resistance (Ω)

Practice Questions

11 Calculate the power supplied to a motor with 7 A of current flowing through it and 2.5 V of potential difference across it. 7 × 2.5 = 17.5 W

12 Calculate the potential difference across a lamp with 0.5 A of current flowing through it and 12 W of power supplied to it. 12/0.5 = 24 W

13 Calculate the current flowing through a lamp with a 95 W power rating and a resistance of 150 Ω.

√95

150 = 0.796 A

14 A printer is supplied with 50 W of power. The current flowing through the printer is measured at 0.25 A. Calculate the potential difference. 50/0.25 = 200 W

15 Calculate the voltage of a battery which supplies 12 J to 6 C. 12/6 = 2 V 16 Calculate the amount of energy delivered by a 4V cell to 8 C. 8 × 4 = 32 J 17 A vacuum cleaner motor is supplied with 2 kW of power and 12 A of current flows. Calculate the

resistance of the motor. 2000/122 = 13.9 Ω

39

The National Grid p189 CGP Knowledge Questions

1 What is the National Grid? 2 Give three examples of times when electricity demand will increase. 3 What is needed to transmit a huge amount of electrical power? 4 What is the problem with using a high current in electrical cables? 5 Describe and explain how this problem is solved. 6 Why must the potential difference be decreased before it goes to consumers? 7 Name the type of transformer used to increase the potential difference in order to transmit the

electricity efficiently. 8 Name the type of transformer used to decrease the potential difference. 9 Name the five parts of the National Grid. 10 Label the following parts of the National Grid below.

40

The National Grid p189 CGP Knowledge Answers

1 What is the National Grid? A system of cables and transformers that connect power stations to consumers of electricity

2 Give three examples of times when electricity demand will increase. When people get up in the morning, return home from work or school, when it is dark or cold outside or when there is a big event being shown on television.

3 What is needed to transmit a huge amount of electrical power? Either a high potential difference of a high current

4 What is the problem with using a high current in electrical cables? A large amount of energy is lost from the cables and transferred into the thermal energy store of the surroundings

5 Describe and explain how this problem is solved. The potential difference is increased to a very high value which keeps the current low which decreases the energy lost into the thermal energy store of the wires and the surroundings.

6 Why must the potential difference be decreased before it goes to consumers? To make it safe to use

7 Name the type of transformer used to increase the potential difference in order to transmit the electricity efficiently. Step-up transformer

8 Name the type of transformer used to decrease the potential difference. Step-down transformer 9 Name the five parts of the National Grid. Power station, step-up transformer, transmission cables,

step-down transformer, consumers of electricity 10 Label the following parts of the National Grid below.

41

The Particle Model and Density of Materials p191-192 CGP Knowledge Questions

1 Identify which state of matter has a fixed, regular arrangement of particles. 2 Describe the movement of particles in a solid. 3 Describe the arrangement of particles in a liquid. 4 Describe the movement of particles in a liquid. 5 Describe the arrangement of particles in a gas. 6 Describe the movement of particles in a gas. 7 Describe what will happen to the movement of gaseous particles if you increase the temperature. 8 Explain, in detail, what causes gas pressure? 9 State and explain what happens to the pressure exerted by a gas when you increase the

temperature. 10 State the density equation, including the possible units. 11 Which state of matter has the highest density? 12 Complete the sentence to explain your answer to Q11: ________ have the highest density

because they have more _________ in a given __________. 13 Describe how to find the density of an irregularly shaped solid object. 14 Describe how to find the density of a liquid

Practice Questions

15 A block of aluminium has a mass of 108 kg, and its volume is 0.04 m3. What is the density of aluminium?

16 A full bucket contains 20 kg of water. What is the volume of the bucket? (Density of water = 1000 kg/m3)

17 A steel cube has sides of length 10 cm. What is its mass? (Density of steel = 7.7 g/cm3)

42

The Particle Model and Density of Materials p191-192 CGP Knowledge Answers

1 Identify which state of matter has a fixed, regular arrangement of particles. Solid 2 Describe the movement of particles in a solid. They vibrate about fixed positions 3 Describe the arrangement of particles in a liquid. Irregularly arranged. Close together but can

slide/move past each other. 4 Describe the movement of particles in a liquid. Can move past each other, move in random

directions at low speed. 5 Describe the arrangement of particles in a gas. Almost no forces of attraction so there is a

random arrangement. 6 Describe the movement of particles in a gas. Particles move freely and randomly. They have a

range of speeds. 7 Describe what will happen to the movement of gaseous particles if you increase the temperature.

They will move faster. 8 Explain, in detail, what causes gas pressure? When particles collide with the walls of their

container, they exert a force. Pressure is force exerted per unit area so in a sealed container the outward gas pressure is the total force exerted by all of the particles in the gas on unit area of the container walls.

9 State and explain what happens to the pressure exerted by a gas when you increase the temperature. Pressure increases. This is because when temperature increases the particles have more energy in their kinetic energy stores. This means the particles will, on average, be moving faster. If the particles travel faster, then they will hit the walls of the container more often in a given amount of time. Each particle will also have a larger momentum so will exert a larger force when they collide with the container. The increased collision frequency and increased momentum both contribute to a greater total force being exerted per unit area which means pressure has increased.

10 State the density equation, including the possible units. Density (kg/m3 OR g/dm3) = mass (kg or g) ÷ volume (m3 or dm3).

11 Which state of matter has the highest density? Solid 12 Complete the sentence to explain your answer to Q11: Solids have the highest density because

they have more matter in a given volume. 13 Describe how to find the density of an irregularly shaped solid object.

a Use a balance to measure its mass b Find the volume of the object by submerging it in a eureka/displacement can filled with

water and collecting the water displaced in a measuring cylinder. c The volume of water displaced is equal to the volume of the object. d Calculate density using density = mass/volume.

14 Describe how to find the density of a liquid a Place a measuring cylinder on a balance and zero the balance. b Pour 10 ml of the liquid into the measuring cylinder and record the mass. c Calculate density using density = mass/volume. d Repeat for 20 ml to 60 ml of liquid and find an average of the calculated densities.

Practice Answers

15 A block of aluminium has a mass of 108 kg, and its volume is 0.04 m3. What is the density of aluminium? 108/0.04 = 2700 kg/m3

16 A full bucket contains 20 kg of water. What is the volume of the bucket? (Density of water = 1000 kg/m3) 20/1000 = 0.02 m3

17 A steel cube has sides of length 10 cm. What is its mass? (Density of steel = 7.7 g/cm3) 7.7 × 103 = 7700 g/cm3

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Internal Energy, Changes of State and Latent Heat p193-194 CGP Knowledge Questions

1 What two types of energy stores of particles contain energy? 2 Define ‘internal energy’ of a system. 3 State what heating a system will do to its internal energy. 4 What two things can happen to a system when it is heated? 5 What is required for a change of state? 6 Name the following changes of state:

Solid to liquid -

Gas to liquid -

Solid to gas -

Liquid to solid -

Liquid to gas – 7 True or false: mass is conserved when matter changes state. 8 Is a change of state a physical or chemical change? 9 Define specific latent heat. 10 Compare specific latent heat of fusion and specific latent heat of vaporisation. 11 State the specific latent heat equation, including units.

Practice Questions

12 The melting point of oxygen is -219 oC, and the boiling point of oxygen is -183 oC. What state will oxygen be in at -200 oC?

13 The graph below shows the temperature of a substance as it heated.

a Identify the states at A, B and C. b Identify the processes at D and E.

14 220 J of energy is required to melt 1.5 kg of a substance. Calculate the specific latent heat of fusion for this substance.

15 How much heat energy is given out when 500 g of steam at 100°C condenses at 100°C? [Specific latent heat of vaporisation of water = 2,260,000 J/kg.]

16 What mass of oxygen can be boiled if, 138 450 J of energy is supplied to liquid oxygen at -183°C? [Specific latent heat of vaporisation of oxygen = 213 kJ/kg]

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Internal Energy, Changes of State and Latent Heat p193-194 CGP Knowledge Answers

1 What two types of energy stores of particles contain energy? Kinetic and potential energy stores 2 Define ‘internal energy’ of a system. Internal energy of a system is the total energy that its

particles have in their kinetic and potential energy stores. 3 State what heating a system will do to its internal energy. Increase it. 4 What two things can happen to a system when it is heated? A change in temperature or a change

of state 5 What is required for a change of state? A substance must be heated enough so that the particles

will have enough energy in their kinetic energy stores to break the bonds holding them together.

6 Name the following changes of state: a. Solid to liquid - melting b. Gas to liquid - condensing c. Solid to gas - sublimation d. Liquid to solid - freezing e. Liquid to gas – boiling or evaporation

7 True or false: mass is conserved when matter changes state. True. 8 Is a change of state a physical or chemical change? Physical (it can be reversed). 9 Define specific latent heat. The energy required to change 1 kg of a substance from one state to

another without changing the temperature. 10 Compare specific latent heat of fusion and specific latent heat of vaporisation. Specific latent heat

for a change of state between solid and liquid is called specific latent heat of fusion whereas the specific latent heat for a change of state between liquid and gas is called specific latent heat of vaporisation.

11 State the specific latent heat equation, including units. Energy (J) = mass (kg) × specific latent heat (J/kg)

Practice Answers

12 The melting point of oxygen is -219 oC, and the boiling point of oxygen is -183 oC. What state will oxygen be in at -200 oC? Liquid.

13 The graph below shows the temperature of a substance as it heated.

a Identify the states at A, B and C. A = solid. B = liquid. C = gas. b Identify the processes at D and E. D = melting. E = boiling.

14 220 J of energy is required to melt 1.5 kg of a substance. Calculate the specific latent heat of fusion for this substance. 220 = 1.5 × L. L = 220 ÷ 1.5 = 146.666666 = 147 J/kg (3sf)

15 How much heat energy is given out when 500 g of steam at 100°C condenses at 100°C? [Specific latent heat of vaporisation of water = 2,260,000 J/kg.] 0.5 x 2,260,000 = 1,130,000 J

16 What mass of oxygen can be boiled if, 138 450 J of energy is supplied to liquid oxygen at -183°C? [Specific latent heat of vaporisation of oxygen = 213 kJ/kg] 138,450/213,000 = 0.65 kg

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Developing the Model of the Atom p195 CGP Knowledge Questions

1 Describe the structure of the atom. 2 Where is almost all of the mass of the atom? 3 What is the average radius of an atom? 4 What is the average radius of a nucleus? 5 How many times smaller is the radius of an atom’s nuclei compared to the entire atom? 6 What is the nucleus of an atom composed of? 7 What do all nuclei of atoms of the same element have in common? 8 How can atoms of the same element differ in mass? 9 What was the plum pudding model of the atom? 10 Where was mass thought to be concentrated in the plum pudding model? 11 What was the nuclear model of the atom? 12 Which experiment brought about the nuclear model of the atom? 13 What was fired at gold foil during this experiment? 14 Where was mass thought to be concentrated in the plum pudding model? 15 Who later adapted the nuclear model, determining that electrons orbit the nucleus at specific

distances? 16 What do electrons orbit the nucleus on? 17 Who discovered the neutron? 18 What happens to an atom’s electrons when electromagnetic radiation is absorbed? 19 What happens if an atom gains energy? 20 What must happen for electrons to move nearer to the nucleus?

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Developing the Model of the Atom p195 CGP Knowledge Answers

1 Describe the structure of the atom. Positively charged nucleus surrounded by negatively charged electrons

2 Where is almost all of the mass of the atom? Nucleus 3 What is the average radius of an atom? 1 × 10-10 m 4 What is the average radius of a nucleus? 1 × 10-14 m 5 How many times smaller is the radius of an atom’s nuclei compared to the entire atom? 10,000

times smaller 6 What is the nucleus of an atom composed of? Protons and neutrons 7 What do all nuclei of atoms of the same element have in common? Same number of protons 8 How can atoms of the same element differ in mass? By having different numbers of neutrons 9 What was the plum pudding model of the atom? The atom as a ball of positive charge with negative

electrons embedded in it 10 Where was mass thought to be concentrated in the plum pudding model? Throughout the atom 11 What was the nuclear model of the atom? A small positively charged nucleus in the centre

surrounded by negative electrons 12 Which experiment brought about the nuclear model of the atom? Alpha particle scattering

experiment 13 What was fired at gold foil during this experiment? Alpha particles 14 Where was mass thought to be concentrated in the plum pudding model? At the centre (nucleus) 15 Who later adapted the nuclear model, determining that electrons orbit the nucleus at specific

distances? Niels Bohr 16 What do electrons orbit the nucleus on? Electron shells or energy levels 17 Who discovered the neutron? James Chadwick 18 What happens to an atom’s electrons when electromagnetic radiation is absorbed? Electrons move

to a higher energy, further from the nucleus 19 What happens if an atom gains energy? The atom’s electrons move to a higher energy, further

from the nucleus 20 What must happen for electrons to move nearer to the nucleus? The atom must release

electromagnetic radiation or lose energy

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Isotopes and Nuclear Radiation p196 CGP Knowledge Questions

1 What do atoms with unstable nuclei give out to become more stable? 2 What is the name of the process in which atoms with less stable nuclei become more stable? 3 What do you call a sample which contains atoms with unstable nuclei? Define ‘activity’. Define

‘count rate’. 4 What are detectors of radiation called? 5 What are the units for activity and count-rate? 6 List the four types of radiation that may be emitted from the nucleus of atoms with unstable

nuclei. 7 State the charges of the four types of radiation. 8 Describe how beta particles are formed and ejected (3 key points). 9 Complete the following table:

Radiation What is it made of?

Range in air

What material (and thickness) will stop it?

Ionising power (Strong, weak or very weak)

Alpha

Beta

Gamma

Practice Questions

10 Fill in the two blank boxes on Figure 1 with either: activity or count rate.

11 Look at Figure 2. Suggest how you would find out whether the source is emitting alpha particles.

Figure 1

Figure 2

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Isotopes and Nuclear Radiation p196 CGP Knowledge Answers

1 What do atoms with unstable nuclei give out to become more stable? Radiation 2 What is the name of the process in which atoms with less stable nuclei become more stable?

Radioactive decay 3 What do you call a sample which contains atoms with unstable nuclei? Radioactive source 4 Define ‘activity’. The rate at which a source of unstable nuclei decays 5 Define ‘count rate’. Number of decays recorded each second by a detector 6 What are detectors of radiation called? Geiger-Muller tubes 7 What are the units for activity and count-rate? Becquerel (Bq) 1 Bq = 1 decay per second. 8 List the four types of radiation that may be emitted from the nucleus of atoms with unstable

nuclei. Alpha particle (α), beta particle (β), gamma ray (γ), neutron (n) 9 State the charges of the four types of radiation. α is +2; β is -1, γ and n have no charge. 10 Describe how beta particles are formed and ejected.

A neutron turns into a proton and electron

The proton remains in the nucleus

The electron is ejected from the nucleus at high speed 11 Complete the following table:

Radiation What is it made of?

Range in air

What material (and thickness) will stop it?

Ionising power (Strong, weak or very weak)

Alpha Two protons & Two neutrons

5 cm Thin sheet of paper Strong

Beta High speed electron

1 m 5 mm aluminium (Al) or 2 mm lead (Pb)

Weak

Gamma Electromagnetic radiation

Unlimited 5 cm of lead (Pb) or 1 m of concrete

Very weak

Practice Answers

12 Fill in the two blank boxes on Figure 1 with either: activity or count rate. Decays recorded by detector: count-rate. Decays in all directions: activity.

13 Look at Figure 2. Suggest how you would find out whether the source is emitting alpha particles. Place paper between the source and Geiger tube. If the Geiger tube records no radiation when paper is used as the absorber, the radiation must be alpha.

Figure 1

Figure 2

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Nuclear Equations p197 CGP Knowledge Questions

1 What is the rule to remember when writing nuclear equations? 2 What are alpha particles made up of? 3 How can an alpha particle be represented in a nuclear equation? 4 Write a general nuclear equation for alpha decay. 5 What is a beta particle? 6 How can a beta particle be represented in a nuclear equation? 7 What happens during a beta decay? 8 Write a general nuclear equation for beta decay. 9 What is a nucleus getting rid of when it releases gamma rays? 10 Why do we not need to write nuclear equations for gamma decay?

Practice Questions

11 Complete the following nuclear equations for alpha decay:

a Bi83211 → Tl___

___ + α____

b Po84204 → Pb___

___ + α____

c Ra86224 → Po___

___ + α____

d U92235 → Th___

___ + α____

e Np________ → Pa91

233 + α____

f At______ → Bi83

211 + α____

12 Balance the following nuclear equations for beta decay:

a C→614 N___

___ + β______

b P→1532 S___

___ + β______

c Ni→2863 Cu___

___ + β______

d Pb→82209 Bi___

___ + β______

e H→______ He2

3 + β______

f Be→______ B5

10 + β______

13 Identify the type of radiation emitted in each of the following nuclear equations:

a Mn→2555 V23

51 +?

b Cd→48112 In49

112 +?

c Po→84209 Pb82

205 +? d Fr→87

223 At85219 +?

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Nuclear Equations p197 CGP Knowledge Answers

1 What is the rule to remember when writing nuclear equations? The total mass and atomic numbers must be equal on both sides

2 What are alpha particles made up of? Two protons and two neutrons

3 How can an alpha particle be represented in a nuclear equation? α24

4 Write a general nuclear equation for alpha decay.

XZA → YZ-2

A-4 + α24

5 What is a beta particle? A fast moving electron

6 How can a beta particle be represented in a nuclear equation? β-10

7 What happens during a beta decay? A neutron in the nucleus turns into a proton and releases an electron.

8 Write a general nuclear equation for beta decay.

XZA → YZ+1

A + β-10

9 What is a nucleus getting rid of when it releases gamma rays? Excess energy 10 Why do we not need to write nuclear equations for gamma decay? There is no change to the

atomic mass or atomic number. Practice Answers

11 Complete the following nuclear equations for alpha decay:

a Bi83211 → Tl81

207 + α24

b Po84204 → Pb82

200 + α24

c Ra86224 → Po84

220 + α24

d U92235 → Th90

231 + α24

e Np_93237 → Pa91

233 + α24

f At85215 → Bi83

211 + α24

12 Balance the following nuclear equations for beta decay:

a C→614 N7

14 + β-10

b P→1532 S16

32 + β-10

c Ni→2863 Cu29

63 + β-10

d Pb→82209 Bi83

209 + β-10

e H→13 He2

3 + β-10

f Be→410 B5

10 + β-10

13 Identify the type of radiation emitted in each of the following nuclear equations:

a Mn→2555 V23

51 +? alpha

b Cd→48112 In49

112 +? beta

c Po→84209 Pb82

205 +? alpha

d Fr→87223 At85

219 +? alpha

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Half-life p198 CGP Knowledge Questions

1 Name the piece of equipment used to measure radiation. 2 What is count rate? 3 Give two reasons why radioactive decay is said to be random. 4 What is activity? What unit is it measured in? 5 What happens to the activity of a radioactive source over time? 6 What is half-life? 7 What percentage of a radioactive sample will be left after one half-life has passed? 8 What percentage of a radioactive sample will be left after two half-lives have passed?

Practice Questions

9 What is the half-life of the radioactive substance in the graph below?

10 What are the half-lives of the two radioactive substances in the graphs below?

11 The initial count rate of a sample is 24,000 Bq. Calculate:

a the final count rate after 4 half-lives. b the ratio of the final count rate to the initial count rate after 4 half-lives have passed.

12 The initial activity of a sample is 50,000 Bq. Calculate: a the final activity after 3 half-lives. b the ratio of the final activity to the initial activity after 3 half-lives.

13 The initial activity of a sample is 640 Bq. Calculate the final activity as a percentage of the initial activity after two half-lives.

14 A sample of strontium-90 has an activity of 5,000 Bq. After 120 years the activity has fallen to 625 Bq. What is the half-life of strontium-90?

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Half-life p198 CGP Knowledge Answers

1 Name the piece of equipment used to measure radiation. Geiger-Muller tube 2 What is count rate? The number of decays per second detected by a detector 3 Give two reasons why radioactive decay is said to be random. Can’t predict exactly which nucleus

in a sample will decay or when any nucleus in a sample will decay. 4 What is activity? What unit is it measured in? The number of decays per second. Unit is the

Becquerel (Bq) 5 What happens to the activity of a radioactive source over time? It will decrease 6 What is half-life? The time it takes for the activity/count rate/number of nuclei/mass of a

radioactive sample to halve. 7 What percentage of a radioactive sample will be left after one half-life has passed? 50% 8 What percentage of a radioactive sample will be left after two half-lives have passed? 25%

Practice Answers

9 What is the half-life of the radioactive substance in the graph below? 6 days

10 What are the half-lives of the two radioactive substances in the graph below? 5700 years and 4500

million years.

11 The initial count rate of a sample is 24,000 Bq. Calculate:

a the final count rate after 4 half-lives. 1,500 Bq b the ratio of the final count rate to the initial count rate after 4 half-lives have passed. 1:16

or 1/16 12 The initial activity of a sample is 50,000 Bq. Calculate:

a the final activity after 3 half-lives. 6250 Bq b the ratio of the final activity to the initial activity after 3 half-lives. 1:8 or 1/8

13 The initial activity of a sample is 640 Bq. Calculate the final activity as a percentage of the initial activity after two half-lives. 25% A sample of strontium-90 has an activity of 5,000 Bq. After 120 years the activity has fallen to 625 Bq. What is the half-life of strontium-90? 40 years

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Irradiation and Contamination p199 CGP Knowledge Questions

1 If an object is irradiated what does that mean? 2 Complete: Irradiating something does not make it...... 3 State two ways to reduce the effects of irradiation. 4 Explain what is meant by contamination? 5 What should be used when handling radioactive sources? 6 What might industrial workers who handle radioactive sources wear? 7 Explain why ionizing radiation is dangerous. 8 What are the most dangerous sources of ionising radiation when outside the body? 9 Explain your answer to question 8. 10 What is the least dangerous source of radiation outside the body? Why? 11 What types of sources pose the greatest danger of irradiation? 12 What type of radioactive source/sources are most dangerous when inside the body? Explain why. 13 Why are the other type/types less dangerous inside the body? 14 What type of source poses the greatest risk from contamination?

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Irradiation and Contamination p199 CGP Knowledge Answers

1 If an object is irradiated what does that mean? It is exposed to a radioactive source. 2 Complete: Irradiating something does not make it...... radioactive 3 State two ways to reduce the effects of irradiation. Keep sources in lead lined boxes and standing

behind barriers when using sources. 4 Explain what is meant by contamination? When unwanted radioactive atoms get onto or into an

object. 5 What should be used when handling radioactive sources? Gloves and tongs 6 What might industrial workers who handle radioactive sources wear? A protective suit 7 Explain why ionizing radiation is dangerous. If ionizing radiation enters living cells then it can

ionize atoms in them. This can damage the cells (causing things like cancer) or kill the cells completely.

8 What are the most dangerous sources of ionising radiation when outside the body? Beta and gamma sources

9 Explain your answer to question 8. Beta and gamma can penetrate the body and get to delicate organs.

10 What is the least dangerous source of radiation outside the body? Why? Alpha, because it can’t penetrate the skin and is easily blocked by a small air gap.

11 What types of sources pose the greatest danger of irradiation? Beta and gamma 12 What type of radioactive source/sources are most dangerous when inside the body? Explain why.

Alpha sources because all their damage is done in a small area 13 Why are the other type/types less dangerous inside the body? Beta are less damaging because the

radiation is absorbed over a wider area and some passes out of the body completely. Gamma are the least dangerous because most of the gamma radiation will pass out of the body and gamma is the least ionising.

14 What type of source poses the greatest risk from contamination? Alpha