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P1 06 Transfer Electrical Energy

253 minutes

255 marks

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(a) (i) Complete the sentence by choosing the correct word from the box.

electrons neutrons protons

An electric current is a flow of ........................................................................(1)

(ii) What is the name and circuit symbol for the instrument used to measure electric current?

Name: ..............................................................................................................

Symbol:

(2)

(b) When an electric current flows through a wire, the wire will get hot. Two of the following make use of this heating effect. Which two?

1. .................................................................................................................................

2. .................................................................................................................................(2)

(c) A 0.2 kW light bulb is switched on for 3 hours.

Use the following equation to calculate, in kWh, how many units of electrical energy are transferred to the bulb during the 3 hours.

units = power × time

....................................................................................................................................

Number of units = kWh .............................(2)

(Total 7 marks)

Q2. A castle is a long way from the nearest town. Batteries power the car park ticket machine. Solar cells are used to keep the batteries charged.

(a) Complete the following sentences by choosing the correct words from the box. Each word may be used once or not at all.

chemical electrical heat light sound

(i) The energy input to the solar cells is ................................................ energy.(1)

(ii) The useful energy output from the solar cells is ........................................ energy.(1)

(b) For every 500 J of energy absorbed by the solar cells, 75 J of energy are transferred to the batteries.

Use the following equation to calculate the efficiency of the solar cells. Show clearly how you work out your answer.

Efficiency =

.....................................................................................................................................

.....................................................................................................................................

Efficiency = ……………………………(2)

(c) Which one of the following statements gives the main reason for using solar cells to charge the batteries?

Tick ( ) the box next to your choice.

Solar cells give a constant supply of electricity.

A few solar cells can provide a large amount of electricity.

The ticket machine is a long way from other electricity supplies. (1)

(d) The graph shows how the cost of producing electricity using solar cells has changed.

Use the graph to predict the cost of one Unit of electricity in 2010.

.....................................................................................................................................(1)

(Total 6 marks)

Q3. (a) List A shows three electrical devices. List B gives different forms of useful energy. Draw a straight line from each of the devices in List A to the useful energy form it produces in List B.Draw only three lines.

(3)

(b) The power of each device is given in the table.

Device Power

Toaster 1.2 kW

Fan 30 W

Personal Stereo

10 W

Which one of the devices will transfer the most energy in 10 minutes?

.....................................................................................................................................(1)

(c) The diagrams show the readings on a domestic electricity meter in April and July.

(i) How many Units (kWh) of electricity were used between the two meter readings?

..........................................................................................................................

..........................................................................................................................

Number of Units = ............................................(1)

(ii) One Unit costs 6p.

Use the following equation to calculate the cost of the electrical energy used between the two meter readings. Show clearly how you work out your answer.

total cost = number of Units × cost per Unit

..........................................................................................................................

..........................................................................................................................

Cost = ..........................................................................(2)

(d) A 3000 watt electric cooker is switched on for 2 hours.

Use the following equation to calculate the number of Units of energy transferred by the cooker. Show clearly how you work out your answer.

energy transferred = power × time(kilowatt-hour, kWh) (kilowatt, kW) (hour, h)

.....................................................................................................................................

.....................................................................................................................................

Energy transferred = ..................................................kWh(2)

(Total 9 marks)

Q4. (a) The drawing shows the energy transferred each second by a television set.

(i) What form of energy is transferred as waste energy by the television set?

..........................................................................................................................(1)

(ii) What effect will the waste energy have on the air around the television set?

..........................................................................................................................(1)

(iii) Use the following equation to calculate the efficiency of the television set.

efficiency =

..........................................................................................................................

..........................................................................................................................

Efficiency = .............................................................(2)

(b) The diagrams show the energy transferred each second for three different types of lamp. For each lamp the electrical energy input each second is 100 joules.

Which type of lamp is the most efficient?

.....................................................................................................................................

Give a reason for your choice.

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 6 marks)

Q5. (a) The picture shows a new washing machine.

Complete the following sentence using one of the words in the box.

kinetic light sound

A washing machine is designed to transform electrical energy into heat and

......................................................... energy(1)

(b) The instruction booklet for the washing machine contains the following information.

Wash cycle Average powerduring cycle

Time taken torun cycle

HOT 1.5 kW 2 hours

COOL 1.1 kW 1½ hours

FAST 1.0 kW ¾ hour

(i) Use the following equation to calculate the energy transferred, in kilowatt-hours, to the washing machine during the HOT wash cycle. Show how you work out your answer.

energy transferred = power × time

...........................................................................................................................

...........................................................................................................................

Energy transferred = .................................... kWh(2)

(ii) Why does it cost more to use the washing machine on the HOT cycle than on the COOL or FAST cycle?

...........................................................................................................................

...........................................................................................................................(1)

(iii) Before buying a washing machine, a householder researched several makes to find out which washing machine was the most energy efficient.

Write down one way that he could have done this research.

...........................................................................................................................

...........................................................................................................................(1)

(Total 5 marks)

Q6. A householder was out shopping when her electricity meter reading should have been taken. The electricity company estimated the reading and sent the following bill. Unfortunately, the bill was damaged in the post.

(a) Use the equation in the box to calculate the cost of the electricity used between 12 June and 13 September.

total cost = number of kilowatt-hours × cost per kilowatt-hour

Show clearly how you work out your answer.

....................................................................................................................................

....................................................................................................................................

Total cost = .................................................

(2)

(b) The estimated reading shown on the bill was not very accurate. The correct reading was 62920.

How many kilowatt-hours of electricity had the householder actually used between 12 June and 13 September?

....................................................................................................................................

....................................................................................................................................(2)

(Total 4 marks)

Q7. The pictures show six different household appliances.

(a) Four of the appliances, including the fan heater, are designed to transform electrical energy into heat.

Name the other three appliances designed to transform electrical energy into heat.

1 .................................................................................................................................

2 .................................................................................................................................

3 .................................................................................................................................(3)

(b) Complete the following sentence using one of the words from the box.

chemical heat kinetic sound

Energy that is not usefully transformed by the fan heater is wasted as

................................................. energy.(1)

(c) The table gives information about two different fan heaters.

Useful energy

transferred eachsecond in joules

Wasted energytransferred eachsecond in joules

Fan heater L 1200 10

Fan heater M 1200 20

Complete the following sentence by drawing a ring around the line in the box that is correct.

Fan heater L

is more efficient than

has the same efficiency as

is less efficient than

fan heater M.

(1)(Total 5 marks)

Q8. The diagram shows the label from a new freezer.

(a) An old freezer has an energy consumption per year of 350 kWh.

Use the equation in the box to calculate the extra cost of using the old freezer for one year compared with using a new ‘A’ rated freezer.


Assume 1 kilowatt-hour (kWh) of energy costs 12 p.


.....................................................................................................................................

.....................................................................................................................................

Extra cost per year = £ ..............................(2)

(b) The price of the new freezer was reduced in a sale.

Reducing the price reduces the payback time for replacing the old freezer from 12 years to 9 years.

Calculate, in pounds, how much the new freezer was reduced in the sale.


.....................................................................................................................................

.....................................................................................................................................

Price reduced by = £ ........................................(2)

(c) An advertisement in a shop claims that:

‘Replacing an old freezer with a new ‘A’ rated freezer will benefit the environment.’

Do you agree that replacing the freezer will benefit the environment?

Answer yes or no. ..............................

Explain the reasons for your answer.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 6 marks

Q9. (a) Each letter A, B, C, D and E represents an energy transformation.

A electrical to gravitational potential

B electrical to heat

C electrical to kinetic

D electrical to light

E electrical to sound

Match each of the following devices to the useful energy transformation that it is designed to make.

Write the correct letter, A, B, C, D or E, in the box below the device. Use each letter once or not at all.

(3)

(b) The bar chart shows the power of three electric kettles.

(i) What is the power of kettle Y?

...........................................................................................................................(1)

(ii) In one week each kettle is used for a total of 30 minutes.

Which kettle costs the most to use?

...........................................................................................................................(1)

(iii) A new ‘express boil’ kettle boils water faster than any other kettle.

Draw a fourth bar on the chart to show the possible power of an ‘express boil’ kettle.(1)

(c) Some friends are going on holiday. They want to be able to boil water to make their own hot drinks. They cannot decide which to take, a travel kettle or a small portable immersion heater that can be placed in a mug.

Travel Kettle• 1 k W element

• Holds 1 litre

• Works on 110 V or 230 V

• Washable water filter

Immersion heater• 0.4 k W element

• Heates up to 0.5 litres of water

• Works on 230 V only

• Small compact size

(i) Give one advantage of taking the travel kettle.

...........................................................................................................................

...........................................................................................................................(1)

(ii) Give one advantage of taking the immersion heater.

...........................................................................................................................

...........................................................................................................................(1)

(Total 8 marks)

Q10. (a) The diagram shows the energy transformations produced by a TV.

(i) Use the information in the diagram and the equation in the box to calculate the efficiency of the TV.

efficiency =


...........................................................................................................................

...........................................................................................................................

Efficiency = ..............................(2)

(ii) What eventually happens to the useful energy transferred by the TV?

...........................................................................................................................

...........................................................................................................................(1)

(b) Electrical appliances left on standby use energy.

The bar chart shows the power for the appliances that one family leaves on standby when they go on holiday.

The family is on holiday for a total of 175 hours.

(i) Use the information in the bar chart and the equation in the box to calculate the energy wasted by leaving the compact stereo on standby while the family is onholiday.

energy transferred(kilowatt-hour, kWh)

= power(kilowatt, kW)

× time(hour, h)


...........................................................................................................................

...........................................................................................................................

Energy wasted = .............................. kilowatt-hours(2)

(ii) Electricity costs 12 p per kilowatt-hour.

Use the equation in the box to calculate the cost of leaving the compact stereo onstandby while the family is on holiday.



...........................................................................................................................

Cost = .............................. p(1)

(c) A headline from a recent newspaper article is shown below.

Explain why leaving appliances on standby damages the environment.

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................

.....................................................................................................................................(2)

(Total 8 marks)

Q11. Electrical appliances that are left on standby still use energy.

The bar chart compares the average amount of ‘standby energy’ wasted each year in every home in five countries.

(i) In which country are the homes that waste, on average, the smallest amount of ‘standby energy’?

Draw a ring around your answer.

Australia France Japan UK USA(1)

(ii) Suggest a reason why an average value is used for the ‘standby energy’ wasted in the homes.

...........................................................................................................................

...........................................................................................................................(1)

(b) (i) Australia has one of the lowest electricity prices in the world.

How does this low price seem to affect the amount of ‘standby energy’ wasted?

...........................................................................................................................

...........................................................................................................................(1)

(ii) In Australia, most electricity is generated in coal-burning power stations.The Australian government wants less electricity to be wasted.

Wasting less electricity would be good for the Australian environment.

Explain why.

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................

...........................................................................................................................(2)

(c) Energy is not usually measured in kilowatt-hours.

Which one of the following units is usually used to measure energy?

Draw a ring around your answer.

hertz joule watt(1)

(d) (i) Electricity in Japan costs the equivalent of 17 pence per kilowatt-hour.

Use the information in the bar chart and the equation in the box to calculate howmuch the ‘standby energy’ used in an average Japanese home costs each year.



Give your answer in pence.

...........................................................................................................................

...........................................................................................................................

Cost = ........................................ pence(3)

(ii) In Japan, the largest proportion of electricity is generated using nuclear fuels.

Which one of the following statements gives a good reason for using nuclear fuels to generate electricity?

Put a tick ( ) in the box next to your answer.

A nuclear power station is very expensive to build.

A small amount of nuclear fuel generates a large amount of electricity.

It is easy to store nuclear waste safely. (1)

(Total 10 marks)

Q12. The diagram shows the energy transformations produced by a TV.

(a) Use words from the diagram to complete the following sentence.

The TV is designed to transform ............................................................ energy into

light and ................................................................... energy.(2)

(b) Which one of the following statements is false?

Put a tick ( ) in the box next to the false statement.

The energy transformed by the TV makes the surroundings warmer.

The energy transformed by the TV becomes spread out.

The energy transformed by the TV will be destroyed. (1)

(c) Two different makes of television, A and B, transform energy at the same rate.Television A wastes less energy than television B.

Complete the following sentence by drawing a ring around the correct line in the box.

Television A has

a higher efficiency than

the same efficiency as

a lower efficiency than

television B.

(1)(Total 4 marks)

Q13. The pictures show three different types of electric heater.

(a) The ceramic heater is run on full power for 5 hours.

Use the following equation to calculate, in kilowatt-hours, the amount of energy transferred from the mains to the heater.



.....................................................................................................................................

.....................................................................................................................................

Energy transferred = .............................. kilowatt-hours(2)

(b) Which heater will be the most expensive to run on its highest heat setting?

.....................................................................................................................................(1)

(c) A heater is needed for a small office.

Comparing each type of heater with the other two, give one advantage of using each type of heater in the office.

oil-filled panel heater .................................................................................................

.....................................................................................................................................

fan heater ....................................................................................................................

.....................................................................................................................................

ceramic heater .............................................................................................................

.....................................................................................................................................(3)

(Total 6 marks)

Q14. The picture shows a food processor, which is used to grate, shred, liquidise and mix food.The table gives some information about the food processor.

Energy input Electrical

Useful energy output Kinetic

Power rating 1200 watts

Efficiency 0.8

(a) The food processor is used for a total of 30 minutes a day.

Calculate the cost of the energy wasted by the food processor each day.

Electricity costs 15 p per kilowatt-hour.

Write down the equations you use, and then show clearly how you work out your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Cost of waste energy = ...................................... p(4)

(b) Explain what happens to the waste energy.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 6 marks)

Q15. The instruction booklet for a washing machine contains the following information.

Wash cycle Average power during cycle

Time taken to run cycle

HOT 1.6 kW 2 hoursCOOL 1.1 kW 1 ¼ hoursFAST 1.2 kW ¾ hour

(a) Electricity costs 15 pence per kilowatt-hour.

Calculate, in pence, the cost of using the washing machine for one HOT wash cycle.

Write down the equation you use, and then show clearly how you work out your answer.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Cost = ................................... pence(2)

(b) Why does it cost more to use the washing machine on the HOT cycle than on the COOL or the FAST cycle?

........................................................................................................................

........................................................................................................................(1)

(Total 3 marks)

Q16. The diagrams in List A show three electrical appliances. Each appliance is designed to transfer electrical energy.

Draw one straight line from each appliance in List A to the useful energy output produced by that appliance in List B.

Draw only three lines.

(Total 3 marks)

Q17. (a) The diagram shows two switches on a room heater. The heater has three power settings. The power produced by two of the settings is given in the table.

Setting Power in watts

Low 700

Medium 1400

High

(i) When both switches are on, the heater works at the high power setting.

What is the power of the heater, in kilowatts, when it is switched to the high power setting?

...............................................................................................................

Power = ......................................................... kilowatts(1)

(ii) The heater is used on the high power setting. It is switched on for 1½ hours.

Use the equation in the box to work out the energy transferred from the mains to the heater in 1½ hours.


Show clearly how you work out your answer and give the unit.

...............................................................................................................

...............................................................................................................

...............................................................................................................

Energy transferred = ....................................................(3)

(iii) This type of heater is a very efficient device.

What is meant by a device being very efficient?

...............................................................................................................

...............................................................................................................(1)

(b) The graph shows how the temperature of a room changes during the 1½ hours that the heater is used.

After 1 hour, the temperature of the room has become constant, even though the heater is still switched on.

Explain why.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 7 marks)

Q18. (a) The diagram shows two switches on a room heater. The heater has three power settings. The power produced by two of the settings is given in the table.

Setting Power in kW

Low 0.5

Medium 1.5

High

(i) When both switches are on, the heater works at the high power setting.

What is the power of the heater when it is switched to the high power setting?

...............................................................................................................

Power = ......................................................... kW(1)

(ii) The heater is used on the medium power setting. It is switched on for three hours.

Use the equation in the box to work out the energy transferred from the mains to the heater in three hours.

energy transferred(kilowatt-hour, kWh)

= power(kilowatt, kW) × time

(hour, h)


...............................................................................................................

...............................................................................................................

Energy transferred = ..................................... kWh(2)

(iii) Electricity costs 12 pence per kilowatt-hour.

Use the equation in the box to calculate how much the heater costs to use onmedium power for three hours.



...............................................................................................................

...............................................................................................................

Total cost = ................................................ pence(2)

(b) The heater is used to warm a room.

The graph shows how the temperature of the room changes from the moment the heater is switched on.

The heater was first used on the medium setting.

(i) At what time was the heater setting changed to the high setting?

..............................................................

Give a reason for your answer.

...............................................................................................................

...............................................................................................................

...............................................................................................................

(2)

(ii) From 7 pm until 10 pm, the temperature of the room is not changing.

Which one of the following statements gives the reason why the temperature of the room is not changing?

Put a tick ( ) in the box next to your answer.

The room is losing energy slower than the heater supplies energy.

The room is losing energy as fast as the heater supplies energy.

The room is losing energy faster than the heater supplies energy.

(1)(Total 8 marks)

Q19. The picture shows a new washing machine. When the door is closed and the machine switched on, an electric motor rotates the drum and washing.

(a) Complete the following sentences.

(i) An electric motor is designed to transform electrical energy into

............................................... energy.(1)

(ii) Some of the electrical energy supplied to the motor is wasted as

....................................... energy and ...................................... energy.(1)

(b) What happens to the energy wasted by the electric motor?

........................................................................................................................

........................................................................................................................(1)

(c) The diagram shows the label from the new washing machine.

An ‘A’ rated washing machine is more energy efficient than a ‘C’ rated washing machine.

Explain what being more energy efficient means.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(d) The graph shows that washing clothes at a lower temperature uses less energy than washing them at a higher temperature. Using less energy will save money.

(i) Electricity costs 12 p per kilowatt-hour (kWh).The temperature setting is turned down from 40 °C to 30 °C.

Use the graph and equation in the box to calculate the money saved each wash cycle.



...............................................................................................................

...............................................................................................................

Money saved = .................................................. p(2)

(ii) Suggest why reducing the amount of energy used by washing machines could reduce the amount of carbon dioxide emitted into the atmosphere.

...............................................................................................................

...............................................................................................................(1)

(Total 8 marks)

Q20. The diagram shows four electrical appliances. Each appliance is designed to transform electrical energy into one form of output energy.

Kettle Toaster RadioHair straighteners

(a) Which one of the appliances is designed to give a different form of output energy from the other three appliances?

..........................................................................................


........................................................................................................................

........................................................................................................................(2)

(b) The power of each appliance is given in the table.

Appliance Power

Kettle 2.5 kW

Toaster 920 W

Radio 15 W

Hair straighteners 75 W

Each appliance is switched on for 5 minutes.

Which appliance transforms the most energy?

..........................................................................................(1)

(c) The 75 watt hair straighteners are switched on for a few minutes each day.In one year, the amount of energy transferred from the mains electricity supply to the hair straighteners is 4 kilowatt-hours.

Electricity costs 15 p per kilowatt-hour.

Use the equation in the box to calculate the yearly cost of using the hair straighteners.



........................................................................................................................

........................................................................................................................

Total cost = ............................................. pence(2)

(d) The graph shows how the time to boil water in an electric kettle depends on the volume of water in the kettle.

A householder always fills the electric kettle to the top, even when only enough boiling water for one small cup of coffee is required.

Explain how the householder is wasting money.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(3)

(Total 8 marks)

Q21.(a) The table gives information about some ways of reducing the energy consumption in a house.

Method of reducing energyconsumption

Installationcost in £

Annual saving onenergy bills in £

Cavity wall insulation 250 115

Jacket for hot water tank 12 35

Upgraded central heating controls 310 80

Show that over 5 years, the most cost-effective method of reducing energy consumption is to install cavity wall insulation.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(b) Any device that transforms energy will waste energy.

Why must the total energy input to such a device always equal the total energy output from the device?

........................................................................................................................

........................................................................................................................(1)

(c) A holiday cottage has a pre-payment electricity meter. The electricity is charged at the rate of 20 p per kWh. A £2 coin is put into the meter and a 2.5 kW fire switched on.

Use the equations in the box to work out how many hours it will be before £2 runs out.Assume that no other electrical device is switched on.




........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Time = ................................... hours(2)

(Total 5 marks)

Q22. The graph shows how the energy transferred by a 2 kW electric kettle varies with the time, in hours, that the kettle is switched on.

(a) In one week, the kettle is used for a total of 1.5 hours.Electricity costs 15 p per kilowatt-hour.

Use the equation in the box to calculate the cost of using the kettle for the week.



........................................................................................................................

........................................................................................................................

Cost = ............................................. p(2)

(b) Draw a new line on the graph to show how the energy transferred by a 1 kW kettle varies with time.

(1)(Total 3 marks)

Q23. A homeowner had a new gas boiler installed.

(a) The following information is an extract from the information booklet supplied with the boiler.

Fuel Natural Gas

Water temperature 60 °C

Energy supplied to gas boiler 8.0 kJ/s (8.0 kW)

Efficiency 0.95

(i) Use the equation in the box to calculate the energy transferred each second by the gas boiler to the water inside the boiler.


...............................................................................................................

...............................................................................................................

Energy transferred by the gas boiler each second = ..................... kJ(2)

(ii) The energy value of the gas used in a home is measured in kilowatt-hours (kWh).

The homeowner has a pre-payment meter and pays £30 into his account. With a pre-payment meter, gas costs 15p per kilowatt-hour.

Use the equations in the box to calculate the total number of hours that the gas boiler would operate for £30.




...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Number of hours = ..................................................(2)

(b) Although the gas boiler is very efficient, some energy is wasted.

Explain what happens to the waste energy.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(Total 6 marks)

Q24. (a) The diagram shows the energy transformations produced by a television.

When the television is working, 1200 joules of energy are supplied to the television every second. The useful energy transferred by the television is 720 joules every second.

(i) Use the equation in the box to calculate the efficiency of the television.


...............................................................................................................

...............................................................................................................

Efficiency = ..................................................(2)

(ii) Use one word from the diagram to complete the following sentence.

The electrical energy that is not usefully transformed by the television is wasted as

............................................................ .(1)

(b) Drawn below are the Sankey diagrams for three televisions, J, K and L.The diagrams are drawn to the same scale.

J

K

L

Which one of the televisions, J, K or L, is the most efficient?

Write your answer in the box.


........................................................................................................................

........................................................................................................................(2)

(c) A homeowner is sent an electricity bill every 3 months. The total amount of electrical energy used during one 3-month period was 800 kilowatt-hours.Electrical energy costs 15p per kilowatt-hour.

Use the equation in the box to calculate the cost of the energy transferred from the mains electricity supply.


Show clearly how you work out your answer and give the unit.

........................................................................................................................

........................................................................................................................

Cost = ..................................................(2)

(Total 7 marks)

Q25.Each letter, A, B, C, D and E, represents an energy transformation.

A electrical to chemicalB electrical to heatC electrical to kineticD electrical to lightE electrical to sound

Match each of the following devices to the useful energy transformation that the device is designed to make.

Write the correct letter, A, B, C, D or E, in the box below each device.

Use each letter no more than once.

Fan Kettle Lamp Radio

(Total 4 marks)

Q26. A student uses an electric motor to lift a load.

In the motor, the electrical energy is transferred into other types of energy. Some of this energy is useful and the rest of the energy is wasted.

(a) (i) Name the useful energy output from the electric motor.

...............................................................................................................(1)

(ii) What eventually happens to the wasted energy?

...............................................................................................................

...............................................................................................................(1)

(b) The graph shows the input energy the motor needs to lift different loads by one metre.

What can you conclude from the graph about the relationship between the load lifted and the input energy needed?

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(c) A shop uses escalators to lift customers to different floor levels. The escalators use electric motors. When the shop is not busy some escalators are turned off. A sign tells the customers that the escalators are turned off to save energy.

(i) Each escalator has one motor with an average power of 4000 W. The motor is turned on for an average of 8 hours each day, 6 days each week. Electricity costs 15 pence per kilowatt-hour.

Calculate the cost of the electricity used in an average week to run one escalator.

Use the correct equation from the Physics Equations Sheet.


...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Cost = ............................................. pence(3)

(ii) Give one environmental advantage to turning off electrical appliances when they are not being used.

...............................................................................................................

...............................................................................................................(1)

(Total 8 marks)

Q27. (a) The bar chart shows the power of three different electric hairdryers.

(i) Which one of the hairdryers, A, B or C, would transfer the most energy in 5 minutes?

Write the correct answer in the box.

(1)

(ii) A small ‘travel’ hairdryer has a power of 500 watts.

Draw a fourth bar on the bar chart to show the power of the ‘travel’ hairdryer.(1)

(b) A family shares the same hairdryer.The hairdryer has a power of 1.2 kW. The hairdryer is used for a total of 2 hours each week.

(i) Calculate how many kilowatt-hours (kWh) of energy the hairdryer transfers in 2 hours.



...............................................................................................................

...............................................................................................................

Energy transferred = .................................................. kWh(2)

(ii) Electricity costs 15 pence per kWh.

Calculate the cost of using the hairdryer for 2 hours.


...............................................................................................................

...............................................................................................................

Cost = .................................................. pence(2)

(Total 6 marks)

Q28. The appliances shown below transfer electrical energy to other types of energy.

(a) The vacuum cleaner is designed to transfer electrical energy to kinetic energy.

Three more of the appliances are also designed to transfer electrical energy to kinetic energy. Which three?

Draw a ring around each correct appliance.3

(b) Which two of the following statements are true?

Tick ( ) two boxes.

Appliances only transfer part of the energy usefully.

The energy transferred by appliances will be destroyed.

The energy transferred by appliances makes the surroundings warmer.

The energy output from an appliance is bigger than the energy input.

(2)(Total 5 marks)

Q29. The data included in the diagrams gives the power of the electrical appliances.

TV160 W

Radiant heater1.0 kW

Hairdryer1100 W

Sandwich toaster1.1 kW

Food processor0.4 kW

Table lamp40 W

(a) (i) Which of the appliances are designed to transform electrical energy to kinetic energy?

...............................................................................................................

...............................................................................................................(1)

(ii) Which of the appliances waste energy as heat?

...............................................................................................................

...............................................................................................................(1)

(b) Leaving the radiant heater switched on is likely to lead to more carbon dioxide being emitted into the atmosphere than leaving the table lamp on for the same length of time.

Explain why.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(c) A homeowner decides to monitor the amount of electrical energy used in his home. He can do this by using the home’s electricity meter or by using a separate electronic device.

The table gives some information about each method.

Electricity meter Electronic device

Records to the nearestkilowatt-hour

Records to the nearest1/100th kilowatt-hour

Homeowner takesreadings at regularintervals

Energy use recordedcontinuously andstored for one year

Displays a graphshowing energy useover a period of time

(i) Complete the following sentence.

The reading given by the electronic device is more .................................................. than the reading given by the electricity meter.

(1)

(ii) Suggest how data collected and displayed by the electronic device could be useful to the homeowner.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(3)

(Total 8 marks)

Q30. The data included in the diagrams gives the power of the electrical appliances.

TV160 W

Radiant heater1.0 kW

Hairdryer1100 W

Sandwich toaster1.1 kW

Food processor0.4 kW

Table lamp40 W

(a) (i) Which appliance is designed to transform electrical energy to light and sound?

...............................................................................................................(1)

(ii) Which two appliances transform energy at the same rate?

.................................................... and ....................................................(1)

(b) During one week, the food processor is used for a total of 3 hours.

(i) Use the equation in the box to calculate the energy transferred, in kilowatt-hours, by the food processor in 3 hours.

energy transferred(kilowatt-hour, kWh) = power

(kilowatt, kW) × time(hour, h)


...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Energy transferred = ................................... kWh(2)

(ii) Electricity costs 15 pence per kilowatt-hour.

Use the equation in the box to calculate the cost of using the food processor for 3 hours.



...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Cost = ................................... pence(2)

(c) A homeowner decides to monitor the amount of electrical energy used in his home.

He can do this by using an electricity meter or by using a separate electronic device.

Electricity meter Electronic device

Records to the nearestkilowatt-hour

Records to the nearest1/100th kilowatt-hour

(i) Use one word from the box to complete the following sentence.

precise reliable valid

The reading given by the electronic device is more ........................ than the reading given by the electricity meter.

(1)

(ii) Monitoring the electrical energy used in a home may help people to save money by encouraging them to use less electricity.

Explain why, apart from saving money, it is important for people to use less electricity.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 9 marks)

Q31. The table gives data about two types of low energy bulb.

Type of bulb Power inputin watts

Efficiency Lifetimein hours

Cost ofone bulb

Compact FluorescentLamp (CFL)

8 20% 10 000 £3.10

Light Emitting Diode(LED)

5 50 000 £29.85

(a) Both types of bulb produce the same useful power output.

(i) Calculate the useful power output of the CFL.



........................................................................................................................

........................................................................................................................

........................................................................................................................

Useful power output = ................................................. W(2)

(ii) Calculate the efficiency of the LED bulb.



........................................................................................................................

........................................................................................................................

........................................................................................................................

Efficiency = ......................................................(1)

(b) Sketch and label a Sankey diagram for the CFL.

(2)

(c) LED bulbs are expensive. This is because of the large number of individual electronicLED chips needed to produce sufficient light from each bulb.

(i) Use the data in the table to evaluate the cost-effectiveness of an LED bulb compared to a CFL.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(ii) Scientists are developing brighter and more efficient LED chips than those currently used in LED bulbs.

Suggest one benefit of developing brighter and more efficient LED chips.

........................................................................................................................

........................................................................................................................(1)

(Total 8 marks)

Q32. The diagram shows how one type of electric storage heater is constructed. The heater has ceramic bricks inside. The electric elements heat the ceramic bricks during the night. Later, during the daytime, the ceramic bricks transfer the stored energy to the room.

(a) In winter, the electricity supply to a 2.6 kW storage heater is switched on each day between midnight and 7 am. Between these hours, electricity costs 5 p per kilowatt-hour.

Calculate the daily cost of using the storage heater.



........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Cost = .................................................. p(3)

(b) Homes with electric storage heaters have a separate meter to measure the electricity supplied between midnight and 7 am. Another meter measures the electricity supplied at other times. This electricity supplied at other times costs 15 p per kilowatt-hour.

Electricity companies encourage people to use electricity between midnight and 7 am by selling the electricity at a lower cost.

Suggest why.

........................................................................................................................

........................................................................................................................(1)

(c) By 7 am, the temperature at the centre of the ceramic bricks is about 800 °C.The temperature of the outside metal casing is about 80 °C.

The ceramic bricks are surrounded by ‘super-efficient’ insulation.

Explain why.

........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................(2)

(d) At 7 am, the electricity supply switches off and the temperature of the ceramic bricks starts to fall. The temperature of the bricks falls by 100 °C over the next four hours. During this time, 9 000 000 J of energy are transferred from the bricks.

Calculate the total mass of ceramic bricks inside the heater.

Specific heat capacity of the ceramic bricks = 750 J/kg °C.



........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Mass = .................................................. kg(2)

(Total 8 marks)

Q33.The diagram shows how one type of electric storage heater is constructed. The heater has ceramic bricks inside. The electric elements heat the ceramic bricks during the night. Later, during the daytime, the ceramic bricks transfer the stored energy to the room.

(a) (i) Complete the following sentences using words from the box.

conduction convection evaporation

Energy is transferred through the metal casing by .....................................

The warm air rising from the heater transfers energy to the

room by ................................................(2)

(ii) The inside of the metal case is insulated.

Which one of the following gives the reason why?

Tick ( ) one box.

To transfer energy from the ceramic bricks to the room faster

To stop energy from the room transferring into the heater

To keep the ceramic bricks hot for a longer time

(1)

(b) In winter, the electricity supply to a 2.6 kW storage heater is switched on for seven hours each day.

(i) Calculate the energy transferred, in kilowatt-hours, from the electricity supply to the heater in seven hours.



...............................................................................................................

...............................................................................................................

Energy transferred = .................................................. kWh(2)

(ii) The electricity supply to the heater is always switched on between midnight and 7 am. Between these hours, electricity costs 5 p per kilowatt-hour.

Calculate how much it costs to have the heater switched on between midnight and 7 am.

...............................................................................................................

...............................................................................................................

Cost = .................................................. p(1)

(c) Between 7 am and 8 am, after the electricity supply is switched off, the temperature of the ceramic bricks falls by 25 °C.

Calculate the energy transferred from the ceramic bricks between 7 am and 8 am.

Total mass of ceramic bricks = 120 kg.Specific heat capacity of the ceramic bricks = 750 J/kg °C.



........................................................................................................................

........................................................................................................................

........................................................................................................................

........................................................................................................................

Energy transferred = .................................................. J(2)

(Total 8 marks)

Q34.The picture shows a washing machine. When the door is closed and the machine switched on, an electric motor rotates the drum and washing.



............................................... energy.(1)


........................................ energy and ........................................ energy.(1)


........................................................................................................................

........................................................................................................................(1)

(c) The graph shows that washing clothes at a lower temperature uses less energy than washing them at a higher temperature. Using less energy will save money.

Temperature setting in °C

(i) Electricity costs 15p per kilowatt-hour (kWh).

The temperature setting is turned down from 40 °C to 30 °C.


total cost = number of kilowatt-hours x cost per kilowatt-hour


...............................................................................................................

...............................................................................................................

Money saved = ...............................................(2)

(ii) Reducing the amount of energy used by washing machines could reduce the amount of carbon dioxide emitted into the atmosphere.

Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 7 marks)

Q35.The picture shows a washing machine. When the door is closed and the machine switched on, an electric motor rotates the drum and washing.



............................................... energy.(1)


........................................ energy and ........................................ energy.(1)


........................................................................................................................

........................................................................................................................(1)

(c) The graph shows that washing clothes at a lower temperature uses less energy than washing them at a higher temperature. Using less energy will save money.

Temperature setting in °C

(i) Electricity costs 15p per kilowatt-hour (kWh).

The temperature setting is turned down from 40 °C to 30 °C.


total cost = number of kilowatt-hours x cost per kilowatt-hour


...............................................................................................................

...............................................................................................................

Money saved = ...............................................(2)

(ii) Reducing the amount of energy used by washing machines could reduce the amount of carbon dioxide emitted into the atmosphere.

Explain why.

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................(2)

(Total 7 marks)

M1. (a) (i) electrons1

(ii) ammeterdo not accept ampmeter

1

must be capital Ahorizontal lines not required no e.c.f.

1

(b) light bulbanswers in either order

1

hairdryer1

(c) 0.6accept correct substitution for (0.2 × 3) 1 markaccept 600 watt hours for 1 mark

2[7]

M2. (a) light1

electrical1

(b) 15% or 0.15correct substitution gains 1 mark only an answer of 15 with no unitor an incorrect unit gains 1 mark an answer of 0.15 given with a unit gains 1 mark

2

(c) the ticket machine is a long way from other electricity supplies1

(d) any figure between 5 and 10 inclusiveunit not required but if given must match numerical answer

1[6]

M3. (a) each correct line scores 1 mark

if more than 3 lines are drawn mark incorrect ones first, to a maximum of 3 lines

3

(b) toasteraccept 1.2 kW

1

(c) (i) 4001

(ii) £24 or 2400pfull credit for their (c)(i) × 6p for full credit the correct numerical answer must have the correct unitan answer of 24 or 2400 with no unit or the incorrect unit scores 1 mark(c)(i) × 6 incorrectly evaluated scores 1 mark

2

(d) 6allow 6000 for 1 markallow 3 × 2 for 1 mark

2[9]

M4. (a) (i) heat1

(ii) temperature increases or (cause) convection (currents)accept gets warmeraccept gets hotter

1

(iii) 60% or 0.660 without % scores 1 mark0.6 with a unit scores 1 mark60 with incorrect unit scores

1 mark

or correct substitution for 1 mark

2

(b) street1

more (energy transferred as) light or less (energy transferred as) heat or usefulenergy output the highest

can only score this mark if first mark scoredall efficiencies calculated correctly score 2nd mark point

1[6]

M5. (a) kineticaccept movement

1

(b) (i) 3 (kWh)allow 1 mark for selecting the correct information

1

(ii) transfers more energyaccept transform or use for transferaccept electricity for energyallow higher (average) power and switched on for more time

2

(iii) any one from:

• use the internet

• brochures

• reading adverts

• visiting shops

• recommendation from friends / plumbers1

[5]

M6. (a) £19.20allow 1 mark for correct substitutionie 160 × 12allow 1 mark for an answer (£)1920an answer of 1920p gains both marksan answer of £40.80 gains both marksallow 1 mark for 340 × 12

2

(b) 340allow 1 mark for correctly using the reading 62580 ie 62920 − 62580accept £40.80 for both marks

2[4]

M7. (a) iron1

hairdryer1

kettleanswers can be in any order

1

(b) sound1

(c) is more efficient than1

[5]

M8. (a) £15allow 1 mark for use of 125 (kWh)allow 1 mark for an answer 1500allow both marks for 1500 pence / pallow 1 mark for correct calculation of annual cost for either freezer (£27 and £42)

2

(b) £45

or their (a) × 3allow 1 mark for correct use of 3allow 1 mark for 12 – 9 = 3

2

(c) any two from:the marks are for the explanation

yes plus explanation

• less electricity / energy needed / usedaccept less energy wasted

• less (fossil) fuels burnedaccept a named fossil fueldo not accept conserving (fossil) fuels

• less polluting gases emittedaccept a named polluting gas / greenhouse gases / carbon emissions / reduce global warmingaccept an answer in terms of nuclear fueleg less nuclear fuel required (1) less nuclear waste (1)

2

or no plus explanation

• old freezer must be disposed of

• hazardous chemicals inside freezeraccept CFC gases

• (lot of) energy used in producing new freezer[6]

M9. (a) electric drill C1

MP3 player E1

toaster B1

(b) (i) 2100no unit required / ignore unitsaccept 2.1 kW must have units for this

1

(ii) Y1

(iii) bar drawn with any height greater than Yignore width of bar

1

(c) (i) any one from:answers must be a comparison

• holds more waterdo not accept 1 litre of water on its own

• works in other countriesaccept a named countryaccept works at 2 voltages

• boils faster

• has a more powerful elementdo not accept 1 kW element on its own

• can filter water1

ignore can wash filter

(ii) any one from:

• it weighs less

• smaller to pack

• cheaper to useanswers must be a comparisonor state why the chosen feature is an advantageaccept boils enough for one drink

1[8]

M10. (a) (i) 0.6accept 60 %allow 1 mark for useful energy = 480answer 0.6 with any unit or 60 gains 1 mark only

2

(ii) transferred to surroundingsaccept goes into the air

accept heats the surroundings upaccept gets spread outaccept transferred into heat (only)do not accept wasted / lost unless qualifieddestroyed negates marktransferred into light / sound negates mark

1

(b) (i) 1.75allow 1 mark for converting to kWanswers of 0.7, 0.525, 0.35, 0.875, 1.05, 5.25 gains 1 markanswers of 1750 or 17.5 gains 1 mark

2

(ii) 21p or £0.21 or their (b)(i) × 121

(c) any two from:

• (more) electricity needs to be generated(more) electricity is being used

• (more) power stations needed

• (more) fossil fuels burntaccept named fossil fuel

• (more) pollutant gases emittedaccept named gasaccept harmful for pollutantaccept greenhouse gasesaccept atmospheric pollutionaccept answer in terms of any form of electricity generation and an associated environmental problem

2[8]

M11. (a) (i) France1

(ii) any one from:

• different homes have different appliances(*)

• different homes have different numbers of appliances(*)(*) accept all homes are different

• standby power not the same for all appliances

• some people will switch appliances offaccept named appliancesaccept people waste different amounts of energy

• homes have different numbers of residents

• can’t measure every (individual) homeaccept any sensible suggestionsdo not accept answers in terms of accurate / precise etc

1

(b) (i) increases amount of energy wastedaccept (encourages) people to leave appliances on (standby)accept increases it

1

(ii) any two from:

• less electricity needed / generated

• fewer power stations needed

• less coal is burneddo not accept coal is non-renewable / running outanswers in terms of fuel stocks neutral

• less pollutant gases producedaccept named gasesaccept harmful for pollutantaccept greenhouse gasesaccept reduce / slow / stop global warmingaccept reduces acid rain

2

(c) joule1

(d) (i) 6800accept £68 for 3 marks an answer of 68 gains 2 marksallow 2 marks for correct substitution ie 400 × 17allow 1 mark for obtaining 400answers of 7480, 4760, 12920, 4080 gain 2 marks

3

(ii) a small . . . . . . electricity1

[10]

M12. (a) electrical1

soundcorrect order only

1

(b) the energy transformed by the TV will be destroyed1

(c) a higher efficiency than1

[4]

M13. (a) 9allow 1 mark for correct substitution(1.8 × 5)an answer of 9000 gains 1 markan answer of 2 or 15 gains 1 mark

2

(b) (3kW) fan heateraccept 3kWaccept the middle one

1

(c)features common to more than one heater, treat as neutral

oil-filled

low level heat

cannot be knocked over / space saving / no trailing wiresdo not accept just wall-mounted

or more control over heat outputdo not accept just 3 heat settings

1

fan

warms (office) rapidly or can be used to cool air (in summer)accept can be used as a fanaccept cool air fan (setting)accept ‘it has a cool air setting in case it gets too hot’do not accept a specific reference to cooling the heater

1

ceramic

can be switched on for set periods of timedo not accept just has a timer

or can be switched on before office is used / switched off automatically at night1

[6]

M14. (a) 1.8 (p)these 4 marks can be broken down as follows:1 mark for correct transformation and substitution into efficiency equationie 0.8 × 1200 – useful powerPLUS1 mark for useful power = 960 W / 0.96 kWPLUS1 mark for waste energy transferred = 0.24 × 0.5orwaste energy transferred = 0.12 (kWh)PLUS1 mark for cost = 0.12 × 15where a mathematical error has been made full credit should be given for subsequent correct method

4

(b) the waste energy is transferred as heat and sound1

to the surroundings where it spreads out / is shared bysurrounding particles

accept air for surroundings1

[6]

M15. (a) 48allow 1 mark for calculating energy as 3.2 kWh

2

(b) largest power and longest time to run1

[3]

M16. 3 lines correct

allow 1 mark for each correct linemore than 1 line drawn from any appliance and all those lines are incorrect

[3]

M17. (a) (i) 2.1correct answer only

1

(ii) 3.15ortheir (a)(i) × 1.5 correctly calculated

allow 1 mark for correct substitutionie 2.1 × 1.5ortheir (a)(i) × 1.5

2

kilowatt-houraccept kWhora substitution 2100 × 5400 scores 1 mark2100 × 5400 incorrectly calculated with answer in joules scores 2marksan answer of 11 340 000 scores 2 marksan answer of 11 340 000 J scores 3 marks

1

(iii) most (input) energy is usefully transformedaccept does not waste a lot of energyaccept most of the output / energy is usefuldo not accept it does not waste energy

1

(b) the room is losing energy / heat1

at the same rate as the heater supplies itthis mark only scores if the first is scoreddo not accept heater reaches same temperature as room / surroundingsrate of heat gain = rate of heat loss scores both marks

1[7]

M18. (a) (i) 2(.0)accept 2000 W or 2000 watt(s)accept answer given in tabledo not accept 2000

1

(ii) 4.5allow 1 mark for correct substitutionie 1.5 × 3allow 1 mark for the answers 1.5 or 6(.0)

2

(iii) 54ortheir (a)(ii) × 12 correctly calculated

allow 1 mark for correct substitutionie 4.5 × 12ortheir (a)(ii) × 12

allow 1 mark if correct answer is given in pounds eg £542

(b) (i) 6 pm1

temperature starts to rise fasteronly scores if 6 pm given

orgraph (line) is steeper / steepest

it refers to graph gradient or temperatureaccept answers in terms of relative temperature riseeg 5 to 6 pm 2 °C rise, 6 to 7 pm 6 °C riseaccept temperature rises sharply / rapidly / quicklydo not accept temperature starts to rise

1

(ii) middle box ticked1

[8]

M19. (a) (i) kineticdo not accept movement

1

(ii) thermalaccept heat for thermal

sounddo not accept noise for soundboth answers required in either order

1

(b) transferred to surroundings / surrounding molecules / atmosphere‘it escapes’ is insufficient

orbecomes dissipated / spread out

accept warms the surroundingsaccept degraded / dilutedaccept a correct description forsurroundings eg to the washing machinedo not accept transformed into heat on its own

1

(c) a smaller proportion / percentage of the energy supplied is wastedowtte

accept a statement such as ‘less energy is wasted’ for 1 markdo not accept costs less to runignore references to uses less energy

2

(d) (i) 2.4 (p)accept 2 p if it is clear from the working out this is rounded from 2.4 pallow 1 mark for correct substitution of correct valuesie 0.2 × 12allow 1 mark for calculating cost at 40 °C (13.2 p)orcost at 30 °C (10.8 p)

2

(ii) any one from:

• less electricity neededignore answers in terms of the washing machine releasing less energyan answer in terms of the washing machine releasing CO2 negates the markdo not accept less energy is produced


• less fuel is burnedaccept a correctly named fueldo not accept less fuel is needed

1[8]

M20. (a) radioradio must be chosen for reason to score

1

gives out soundinclusion of other forms of energy negates mark

orothers give out heat / thermal energy

1

(b) Kettleaccept 2.5 (kW)

1

(c) 60 (p)

accept £0.6(0)allow 1 mark for correct substitution ie 4 × 15substitution only scores if no subsequent step shown£60 scores 1 mark

2

(d) (bigger volume) takes more time (to boil)accept explanation using data from graph

1

(so) more energy transferreddo not accept electricity for energy

1

(and) this costs more moneyignore references to cost of water

1[8]

M21. (a) total saving shown for each methodie:cavity wall £325jacket £163central heating £90

allow 1 mark for one correctly calculated valueorallow 1 mark for showing energy bill savings for each method over 5 yearsie:cavity wall £575jacket £175central heating £400there are no marks for calculation of payback time

2

(b) energy cannot be destroyedaccept energy is conservedignore reference to created

1

(c) 4 (hours)allow 1 mark for obtaining number of kWh = 10or energy transferred = 10

2[5]

M22. (a) 45(p)accept £0.45 for both marksallow 1 mark for correct substitution ie 3 × 15do not award any marks if 45 is used in a subsequent calculation to obtain a final answer

2

(b) straight line drawn from origin passing through (1,1)line must reach 1,1 but does not need to continue beyond

1[3]

M23. (a) (i) 7.6allow 1 mark for correct substitution and / or transformation

ie 95 × 8.0

2

(ii) 25 (hours)allow 1 mark for obtaining number of kWh = 200an answer of 26(.3) gains both marks

2

(b) any two from

• transferred to the surroundings / air / atmosphere

• becomes spread out

• shared between (many) molecules

• (wasted as) heat / sound2

[6]

M24. (a) (i) 0.6or60%

allow 1 mark for correct substitution ie provided no

subsequent step shownan answer of 0.6 / 60 with a unit gains 1 mark onlyan answer of 60 gains 1 mark only

2

(ii) heatallow thermal

1

(b) Kreason only scores if K is chosen

1

smallest amount of wasted energyreasons must be comparativeaccept waste arrow is narrowest

orlargest amount of useful energy

accept useful arrow is widestwaste arrow is smallest is insufficient

1

(c) 12 000 por£120

to score both marks the unit must be consistent with the numerical answeranswers 12 000 and 120 gain 1 mark onlyallow 1 mark for correct substitution ie 800 × 15 or 800 × 0.15provided no subsequent step shown

2[7]

M25.Fan C1

Kettle B1

Lamp D1

Radio E1

[4]

M26. (a) (i) kinetic (energy)allow gravitational potential (energy) / gpemovement is insufficient

1

(ii) dissipates into the surroundingsallow warms up the surroundings / air / motoraccept lost to the surroundingsaccept lost as heatignore reference to soundit is lost is insufficient

1

(b) energy (required) increases with loadaccept positive correlationdo not accept (directly) proportional

1

further amplification eg increases slowly at first (or up to 4 / 5 N), then increases rapidly

simply quoting figures is insufficientan answer that only describes the shape of the line gains no marks

1

(c) (i) E = P × t

2880accept £28.80 for all 3 marksan answer £2880 gains 2 marksallow 1 mark for obtaining 48 h or converting to kWallow 2 marks for correct substitutionie 4 × 48 × 15note: this substitution may be shown as two stepsan answer 2 880 000 gains 2 marksan answer £4.80 / 480 gains 2 marksan answer of 192 (ie calculation of energy without subsequent calculation of cost) gains 1 mark)

3

(ii) any sensible suggestion eg

conserves fossil fuels

less (fossil) fuels burned

less pollutant gas (produced)accept a named pollutant gas

less greenhouse gas (produced)saves energy is insufficient

1[8]

M27. (a) (i) A1

(ii) bar drawn with correct heightignore width of bar

1

(b) (i) E = P × t

2.4allow 1 mark for correct substitutionie 1.2 × 2provided no subsequent step shown

2

(ii) 36 or their (b)(i) × 15 correctly calculated

or

their (b)(i) × 0.15 correctly calculated with an answer given in £allow 1 mark for correct substitutionie 2.4 × 15ortheir (b)(i) × 15allow 1 mark for correct substitutionprovided no subsequent step shownan answer £0.36 gains both marks

2[6]

M28. (a) fan1

drill1

washing machinefour circled including correct three scores 1 markfive circled scores zero

1

(b) Appliances only transfer part of the energy usefully1

The energy transferred by appliances makes the surroundings warmer1

[5]

M29. (a) (i) food processorhairdryer

both required and no othereither order

1

(ii) TVTable lampFood processor

all required and no otherany order

1

(b) any two from:

• transfers / requires / uses more energy / poweraccept more electricity usedaccept higher power

• more electricity needs to be generated

• more (fossil) fuels (likely) to be burntaccept a named fossil fuel

2

(c) (i) precisethis answer only

1

(ii) any three from:

• can look for trends / patterns

• help reduce energy use / consumption

• reduce billsaccept save money

• identify appliances which use a lot of energy

• replace appliances with more efficient ones

• see effect of leaving appliances on (standby)to monitor usage is insufficientanswers in terms of environment are insufficient

3[8]

M30. (a) (i) TV1

(ii) hairdryer and sandwich toasterboth required either order but no others

1

(b) (i) 1.2allow 1 mark for correct substitutionie 0.4 × 3 provided that no subsequent step is shown

2

(ii) 18accept £0.18 for both marks

ortheir (b)(i) × 15 correctly calculated

an answer 0.18 scores 1 markallow 1 mark for correct substitutionie 1.2 or their (b)(i) × 15 provided that no subsequent step is shown

2

(c) (i) preciseaccept any correct indication

1

(ii) any two from:

• less electricity needs to be generated

• less fuels neededaccept a named fuel used in any type of power station

• less air / atmospheric pollutionaccept named pollutant eg CO2

accept reduces carbon / carbon dioxide emissionsaccept reduces radioactive waste

• (non-renewable) energy sources last longeraccept running out of fossil fuels / a named fossil fuel

• slows global warming / greenhouse effectdo not accept stops global warmingenvironmentally friendly is insufficientless pollution is insufficient

2[9]

M31. (a) (i)

1.6 (W)

allow 1 mark for correct substitution ie 2

(ii)

32 (%) / 0.32ortheir (a)(i) ÷ 5 correctly calculated

ignore any units1

(b) two output arrowsone arrow should be wider – judged by eye

1

narrower arrow labelled light or useful (energy / output / power)only scores if first mark awarded

and

wider arrow labelled waste (energy / output / power)accept heatignore numerical values

1

(c) (i) any two from:

• comparison over same period of time of relative numbers of bulbs required eg over 50 000 hours 5 CFL’s required to 1 LEDaccept an LED lasts 5 times longer

• link number of bulbs to cost eg 5 CFL’s cheaper than 1 LEDan answer in terms of over a period of 50 000 hours CFLs cost

£15.50 (to buy), LED costs £29.85 (to buy) so CFLs are cheaper scores both marksan answer in terms of the cost per hour (of lifetime) being cheaper for CFL scores 1 mark if then correctly calculated scores both marks

• over the same period of time LEDs cost less to operate (than CFLs)2

(ii) any one from:

• price of LED bulbs will dropdo not accept they become cheaper

• less electricity needs to be generatedaccept we will use less electricity

• less CO2 produced

• fewer chips needed (for each LED bulb)

• fewer bulbs required (for same brightness / light)

• less energy wasteddo not accept electricity for energy

1[8]

M32. (a) E = P × t

91 (p)an answer £0.91 gains 3 marksan answer 0.91 gains 2 marksallow 2 marks for energy transferred = 18.2 (kWh)orsubstitution into 2 equations combined, ie 2.6 × 7 × 5allow 1 mark for correct substitution into E = P × t, ie E = 2.6 × 7orallow 1 mark for multiplying and correctly calculating an incorrect energy transfer value by 5

3

(b) answers should be in terms of supply exceeding demandaccept there is a surplus / excess of electricity (at night)

1

(c) reduce (rate of) energy transfer (from ceramic bricks)accept heat for energydo not accept no energy / heat escapes

do not accept answers in terms of lost / losing heat if this implies heat is wasted energy

1

so keeping the (ceramic) bricks hot for longeraccept increase time that energy is transferred to the roomaccept keep room warm for longer

or

to stop the casing getting too hotaccept so you do not get burnt (on the casing)

1

(d) E = m × c × θ

120allow 1 mark for correct substitutionie 9 000 000 = m × 750 × 100

2[8]

M33. (a) (i) conduction1

convection1

correct order only

(ii) to keep the ceramic bricks hot for a longer time1

(b) (i) E = P × t

18.2allow 1 mark for correct substitution ie 2.6 × 7 provided that no subsequent step is shown

2

(ii) 91 (p)or their (b)(i) × 5 correctly calculated

accept £0.91do not accept 0.91 without £ sign

1

(c) E = m × c × θ

2 250 000allow 1 mark for correct substitution ie 120 × 750 × 25 provided that

no subsequent step is shownanswers 2250 kJ or 2.25 MJ gain both marks

2[8]

M34.(a) (i) kineticdo not accept movement

1

(ii) thermal soundaccept heat for thermal do not accept noise for soundboth answers required in either order

1



accept warms the surroundingsaccept degraded / dilutedaccept a correct description for surroundings eg to the washing machinedo not accept transformed into heat on its own

1

(c) (i) 3 (.0 p)allow 1 mark for correct substitution of correct values ie 0.2 x 15allow 1 mark for calculating cost at 40°C (16.5p)orcost at 30°C (13.5p)

2

(ii) any two from:

• less electricity neededignore answers in terms of the washing machine releasing less energy an answer in terms of the washing machine releasing CO2 negates mark do not accept less energy is produced


• less fuel is burnedaccept a correctly named fuel do not accept less fuel is needed

2[7]

M35.(a) (i) kineticdo not accept movement

1

(ii) thermal soundaccept heat for thermal do not accept noise for soundboth answers required in either order

1



accept warms the surroundingsaccept degraded / dilutedaccept a correct description for surroundings eg to the washing machinedo not accept transformed into heat on its own

1

(c) (i) 3 (.0 p)allow 1 mark for correct substitution of correct values ie 0.2 x 15allow 1 mark for calculating cost at 40°C (16.5p)orcost at 30°C (13.5p)

2

(ii) any two from:

• less electricity neededignore answers in terms of the washing machine releasing less energy an answer in terms of the washing machine releasing CO2 negates mark do not accept less energy is produced


• less fuel is burnedaccept a correctly named fuel do not accept less fuel is needed

2[7]

E1. Although the majority of candidates scored high marks in this question, there were two common errors. These were the suggested use of a voltmeter to measure current and the

microwave oven being linked to the heating effect of an electric current. In most cases the calculation in part (c) was completed correctly.

E2. In part (a) most candidates identified the correct energy form. In part (b) although there were many correct substitutions into the given equation there were few correct evaluations. A significant number of candidates did however give an incorrect answer of 500 / 75. The answers to part (c) seemed equally split between the three possible responses. In part (d) most candidates were able to extrapolate the graph line to give an acceptable answer.

E3. (a) Most candidates showed a good working knowledge of the useful energy produced by a domestic electrical device, although a number of candidates believed that fans usefully produced heat and toasters light.

(b) Candidates were less adept at differentiating between watts and kilowatts. Rather surprisingly there was a small number of ‘personal stereos’ given for the answer which is difficult to understand.

(c) Although this part produced many correct readings of the domestic electricity meter, candidates seemed to experience difficulty in multiplying the numbers in parts (c)(ii) and (d) to successfully provide a cost for the electrical consumption or the energy transferred by the electric cooker.

(d) The answer 6000 for this part was much more common than 6.

E4. Many candidates excellently completed this question. Efficiency can be a difficult concept but the format of the question allowed candidates to demonstrate their understanding.

(a) In part (iii) the main errors involved either 400 being used as the total energy supplied or the correct numerical answer being offered but with the unit J added.

(b) Only a few candidates lost one of the marks by not making their answer comparative.

E5. In part (a) the vast majority of the candidates showed an understanding of energy transfer

and many successfully achieved maximum marks for the calculation in part (b)(i). However, the cost implications of using different power cycles for the washing machine were not widely understood and many candidates were unable to describe how they would undertake research to compare the energy efficiency of domestic appliances. The candidates that were successful generally stated using the Internet.

E6. (a) Although many candidates could correctly manipulate the data to arrive at the figure 1920, many candidates either omitted the decimal point or omitted to state whether the figure was in pounds or pence. Some candidates are apparently unperturbed at the prospect of paying a quarterly bill of £1920.

(b) A third of candidates were able to work out the correct value of 340 kilowatt-hours. Many candidates incorrectly added the two readings together.

E7. (a) Most candidates could correctly name the other three appliances designed to transform electrical energy into heat. A few included the fan heater amongst their choices which was given in the question and a very small number wrote down the names of appliances that were not shown in the pictures.

(b) Most candidates correctly chose sound energy as being the form in which the fan heater wasted energy. A few however selected heat, perhaps thinking that this is always the answer to a ‘wasted energy’ question.

(c) The majority of candidates correctly identified that fan heater L was more efficient than fan heater M.

E8. (a) Most candidates knew how to answer this, but a significant number failed to realise that their answer of ‘1500’ was pence, not pounds.

(b) This proved to be a difficult question for many candidates, a significant number not attempting it. Of those who made an attempt, quite a few realised that there was a saving of 3 years, but did not link the pay-back time to their previous answer.

(c) Most candidates opted for the ‘yes’ answer, gaining some credit for stating that less electricity would be used by the new freezer, but often failing to describe how this would benefit the environment. Of those who chose the ‘no’ option some credit was usually gained for the ideas that the appliance would need to be disposed of.

E9. (a) Most candidates were able to match the energy changes to the correct electrical device.

(b) (i) The majority of candidates correctly stated that the power of kettle Y was 2100 watts. Some however had difficulty in interpreting the scale on the graph and reported the power as 2010 watts. A few candidates reported the power as 2.1 but then forgot to state that the power would then be in kilowatts.

(ii) Most candidates realised that kettle Y would cost the most to use. (b)(iii) Most candidates correctly showed an extra bar on the chart that was higher than for any of the other kettles. A few however, drew a bar that was shorter than the others, perhaps because they confused power with time taken to boil.

(c) Some candidates were unclear as to the difference between an advantage and a disadvantage. Others did not realise that, when asked for an advantage, what is required is a statement as to why one device is better than the other. Although many candidates were able to give a correct advantage for each device, many others failed to indicate any comparison between the two.

E10. (a) (i) This calculation was correctly done by most candidates. Of those who did not score full marks, some gained credit for calculating the useful energy as 480 J, but were then unable to complete the calculation correctly. Others arrived at the correct numerical answer, but added an incorrect unit such as J or J/s.

(ii) A wide range of responses was seen. A number of answers had the energy changing into light/sound and therefore being used by the person watching the television. There were indications that many candidates had not read the question carefully enough to appreciate that it referred to the ‘useful’ energy and what happens to it ‘eventually’.

(b) (i) Just under half of the candidates gained full marks. The most common incorrect answer was 1750 showing no conversion from watts to kilowatts. Many candidates did not read the question carefully and instead of referring to the compact stereo, chose another item or all of the items together.

(ii) The candidates that answered correctly in part (b)(i) generally scored this mark. Many candidates scored the mark for error carried forward mostly from an answer of 1750. A significant but small number of candidates made errors on converting pence to pounds or multiplied by 0.12 but forgot to put in £ sign. Some candidates who had failed to do the correct conversion in part (b)(i) arrived at a cost of £210 for leaving a small electrical item on standby for about a week!

(c) This was very well answered by many candidates. A common mistake seen was that the

electrical appliance itself was giving off heat, which contributed to global warming, or more bizarrely, was giving off carbon dioxide.

E11. (a) (i) Most candidates were able to identify France as being the country with the smallest amount of standby energy.

(ii) Few candidates were able to offer a sensible suggestion as to why an average value of the standby energy is used.

(b) (i) The majority of candidates were able to spot the correct relationship and gain credit. However a significant minority of candidates clearly misunderstand the term ‘standby energy’ believing it to be some kind of reserve store of energy that could be used if the mains supply failed.

(ii) Only the better candidates were able to score both marks for this question. Many answers were very vague and simply talked about there being less pollution, without specifying what type of pollution would be reduced. There were many answers that talked about the general benefits of conservation, and the fact that the coal would one day run out did not answer the question that asked for an explanation of how the environment would benefit.

(c) Surprisingly only half the candidates identified the joule as being the usual unit of energy.

(d) (i) It was encouraging to see that a large number of candidates were able to complete the calculation correctly and earn all three marks available. Many of the weaker candidates were able to substitute the correct numbers into the equation that was given, but then failed to complete the arithmetic correctly nevertheless, they could still score marks by showing the correct method.

Some candidates converted their answer into pounds, but then failed to put a pound sign in front of the number. This lost them a mark as the units ‘pence’ had already been put into the answer line for them.

(ii) Most candidates correctly identified an advantage of using nuclear fuels.

E12. (a) The vast majority of candidates knew that a television is designed to transform electrical energy into light and sound energy.

(b) Most candidates could identify the false statement from the list.

(c) Most candidates realised that wasting less energy leads to a higher efficiency.

E13. Foundation Tier

(a) Most candidates could substitute the correct numbers into the equation, although some erroneously put in a figure of 8 hours instead of 5. The most common mistake was to fail to convert 1800 watts into 1.8 kilowatts, thus arriving at an answer of 9000 instead of 9.

(b) Many candidates chose the ceramic heater, perhaps because it appeared to have the largest number attached to it.

(c) Most candidates were able to score at least one mark on this question, although very few scored all three marks. The most common mistake was simply to pick a feature from the illustration and copy it down. These candidates failed to realise that (i) it should be a feature not possessed by either of the other two, and (ii) that they should explain why this feature is an advantage.

Higher Tier

(a) A large number of candidates scored at least 1 of the 2 marks, common mistakes were a failure to convert from W to kW, or wrongly converting by dividing by 100. A surprising number of answers used the time as 8 hours, presumably because of the 8-hour timer. It would appear that many candidates do not read the questions thoroughly.

(b) This was well answered on the whole, although it appeared that some candidates just looked for the highest number, regardless of units.

(c) Many marks were lost by candidates not comparing each heater with the other two, again an example of not reading the question thoroughly. Good answers explained why the feature would be an advantage rather than just picking out a statement from the lists given.

E17. (a) (i) The majority of candidates indicated that they had correctly added together 1400 and 700 to get 2100. However, a large number of candidates failed to notice that the values given were in watts and that the question asked for the answer in kilowatts.Of those who made an attempt to convert their answer, a large number of candidates were unable to do this correctly, the most common mistakes being to divide by 100 or to multiply by 1000. Another frequently seen error was an indication of 2100/1000 but then a failure to calculate this correctly.

(ii) It was pleasing to see so many correct answers to this calculation, usually by those candidates who opted to work out the energy in kilowatt-hours.Of those candidates who opted for joules, a common mistake was to multiply the power by a time of 90 minutes rather than converting to seconds.

(iii) This question was correctly answered by three fifths of the candidates. Most of the

candidates who failed to score the mark had either just defined the term efficiency or had not picked up on the question asking for .‘very’ efficient.

(b) This part question was correctly answered by only a very small minority of candidates (less than one twentieth). Incorrect responses often stated that the temperature of the room had become the same as the temperature of the heater.

E18. (a) (i) Surprisingly, only just over half of the candidates realised that the high setting would be obtained by adding together the low setting and the medium setting. Some candidates were looking for a pattern and, thinking that each power increased by 1.0, arrived at the answer 2.5.

(ii) Pleasingly nearly three quarters of candidates were able to complete this calculation correctly.

(iii) Only the better candidates could arrive at the correct answer to this calculation. Many candidates simply multiplied the cost per kilowatt-hour by the number of hours instead of by the number of kilowatt-hours, thus arriving at an answer of 36.

(b) (i) Generally most candidates opted for the correct answer of 6.00 pm, although the reason given was often too vague to deserve a mark. Candidates often stated that .that was when the temperature went up., in spite of the fact that the temperature had been increasing throughout the previous hour. A common mistake was to say that the heater was switched on at 7.00 pm because ‘that was when the temperature was the hottest’.

(ii) Just over two thirds of candidates realised that if the temperature of the room was not changing then the room is losing energy as fast as the heater supplies energy.

E19. (a) (i) Kinetic energy was correctly identified by most candidates.

(ii) Most candidates correctly stated that sound and thermal / heat were the two forms of wasted energy.

(b) This was poorly answered, with only just over a quarter of candidates realising that the energy was transferred to the surroundings.

(c) Most candidates were able to earn 1 mark here for stating that the more efficient machine would waste less energy. Very few candidates answered in terms of the proportion of the input energy that was wasted was less.

(d) (i) Few candidates were able to score both marks here. Many of the weaker candidates had difficulty in placing the decimal point correctly. Another common mistake was to calculate the cost for either 40 °C or for 30 °C, but not work out the difference.

(ii) Few correct answers. Many candidates thought that washing machines produced carbon dioxide directly.

E20. (a) The great majority of the candidates knew that the radio was designed to give a different form of output energy from the other three devices. However, not so many could give a correct reason.

(b) About half of the candidates correctly identified the kettle as being the appliance that transforms the most energy. The other half tended to choose toaster, presumably because it had the largest number associated with it and not noticing that the kettle’s power was given in kilowatts rather than in watts.

(c) The majority of candidates arrived at the correct answer of 60 pence. Some candidates thought that the answer was £60.

Of the candidates who arrived at the wrong number because of faulty arithmetic, many of those who showed their working were able to score one mark. This of course was not true for those who failed to show any working.

(d) This question proved to be a good discriminator, with only the best candidates scoring all three marks. About half of the candidates scored two out of the three marks available.

One of the most common reasons for failing to obtain maximum marks was to talk about ‘electricity being wasted’, rather than referring to the amount of energy required to boil the water for a longer period of time. Some of the candidates were also referring to the cost of the extra volume of water rather than the cost of the extra energy required.

E21. (a) Many candidates answered this well. A common error was failing to realise that the question had referred to a period of 5 years; also, simple arithmetical mistakes were not uncommon, particularly when subtracting the installation cost from the energy saving. A significant number of candidates made up their own question and worked out payback times.

(b) Just under half of the candidates were able to state that energy cannot be destroyed or that energy is conserved.

(c) Candidates generally found this calculation difficult, as they had to work back from the cost. Very few seemed to be able to do this in a logical way. A common incorrect response was 10 hours, indicating that perhaps candidates realised they could get 10 kWh for their £2; however, calculations were often just a jumble of numbers, so it was difficult to credit any steps in the working.

E22. (a) The better candidates correctly calculated the answer to be 45 pence. However, many candidates simply multiplied the time (1.5) by the cost per kWh (15) giving an answer of 22.5. Perhaps this was because these numbers were closest to the answer line, and they had not spotted, in the line above the graph, that this was a 2 kW kettle.

(b) Nearly two-fifths of candidates failed even to attempt to draw a line on the graph. Of those who did, most failed to start the line at the origin.

E23. (a) (i) The vast majority of students attempted this calculation, with over three quarters getting the correct answer. The most common errors were in transposing the equation incorrectly, or including the water temperature of 60°C in the calculation.

(ii) Around half of the students were able to use the total cost of £30 and the cost per kWh of 15p to calculate a figure of 200; however that is the point at which most stopped, quoting an answer of 200 hours. A few then attempted to involve the power, with only a minority ending up with the correct answer. A few students did not attempt to answer this question.

(b) Most students gave at least one correct point in answer to this question, with around half being able to give two points correctly.

E24. (a) (i) There were many correct answers here. Use of ‘J’ as a unit for the answer was the most common error.

(ii) Most students correctly identified ‘heat’ as the wasted energy.

(b) Most students correctly gave ‘K’ as the most efficient TV. Of those students, nearly three quarters then went on to supply a correct reason for their choice. Students who simply quoted values from the Sankey diagrams and attempted no comparison did not score the second mark.

(c) Most students were able to multiply the number of kWh by the cost per kWh to get 120 or 12 000. However less than a half of those students were able to give the appropriate unit to match their numerical answer.

E25. Most students scored 4 marks.

E26. (a) (i) This was well answered with most students scoring the mark.

(ii) almost two-thirds of students answered this question correctly. There were some pleasing answers referring to the dissipation of energy into the surroundings.

(b) The majority of students were able to identify the basic pattern of input energy increasing with increasing load. However, only a tenth of students were able to provide further amplification relating to the shape of the graph.

(c) (i) A large number of students were able to identify the correct equation, but mistakes were often made in not converting (or wrongly converting) watts to kilowatts. Most students scored at least one mark.

(ii) The majority of students scored this mark, however a significant number of students failed to realise that an environmental advantage was required, giving a response of ‘to save money’.

E27. (a) (i) Nearly all students correctly identified hairdryer A.

(ii) The great majority of students could correctly complete the bar chart.

(b) (i) Surprisingly, less than two-thirds of students were able to calculate the correct answer. Of those that gave an incorrect answer, only a tiny proportion showed a correct substitution to score one mark.

(ii) Only the better students correctly completed this calculation. Many simply multiplied the time in hours by the cost in pence, as these were the two numbers that appeared in the stem of this part of the question.

E28. (a) Surprisingly, less than two-thirds of students could identify the fan, the drill and the

washing machine as being the devices that were designed to transfer electrical energy to kinetic energy.

(b) Just over half of students scored both marks, and just under half scored one mark.

E29. (a) (i) Most students chose only one appliance to match the criteria given, rather than the two appliances required.

(ii) Most students chose only one appliance to match the criteria given, rather than the three appliances required.

(b) Many students were able to gain one mark for realising that the heater had a higher power than the lamp. Few students were then able to link this with power stations generating more electricity and therefore burning more fossil fuels. A common misconception is that when the appliance transforms energy as heat, carbon dioxide is also given off at the same time.

(c) (i) Responses were fairly evenly divided between ‘precise’ (correct), ‘accurate’ and ‘reliable’.

(ii) There were many pleasing answers relating to how the homeowner could make use of the data collected to reduce energy consumption and lower their energy bills. However, there were also a large number of responses which merely copied the information given in the question; students should realise that this will not gain them marks.

E30. (a) (i) Most students correctly chose the TV.

(ii) Just over 50% of students did not appear to realise that 1100 W and 1.1 kW were the same power rating.

(b) (i) Many students were able to calculate the energy transferred. A minority thought, incorrectly, that they had to convert kilowatts into watts first.

(ii) After scoring two marks for a correct answer in part (b)(i), most students failed to calculate the cost correctly in part (b)(ii). Only a minority managed to get 18 p as their answer. A very common error was to multiply the time (3 hours) by the cost per kWh (15 p) to get 45 p.

(c) (i) Nearly 80% of students gained this mark.

(ii) Answers such as ‘good for the environment’ or ‘eco-friendly’ were often given. These

answers are considered too vague to gain credit in a physics examination. Many students managed to get one mark in this question, normally by linking the use of less electricity to the slowing of global warming or the greenhouse effect. However, few answers were seen that were worthy of two marks.

E31. (a) (i) Almost a half of students gained both marks. The common errors were to multiply 8 by 20 without then dividing by 100 or divide 20 by 8 giving an answer of 2.5.

(ii) A significant number of students thought this question could not be answered due to lack of data. These students had failed to read the question stem that told them both bulbs had the same useful power output. Students scoring both marks in part (a)(i) usually also scored this mark. However, there were a significant number of students giving answers in excess of 100 %.

(b) Students presented numerous versions of a Sankey diagram. Some students failed to label the two outputs and so limited themselves to one mark. A number of students gave three output arrows. Students would be well advised to spend some time practising drawing neat, labelled diagrams.

(c) (i) Students were asked to use the data and not simply to repeat it. However, there were many good answers that compared the cost over the same period of time and gained both marks. Different, but still valid answers, which used correct calculations in terms of cost per hour or hours per pound spent, were regularly seen.

(ii) There was a wide variety of answers, many unfortunately, too vague to credit. The most popular correct answer was in terms of ‘waste less energy’.

E32. (a) Many students gained full credit, or at least two marks, for calculating energy as 18.2 kWh. The most common errors were to use an incorrect time, six hours being popular and / or to calculate cost by dividing 18.2 by 5.

(b) This was very poorly answered, with just under a tenth of students scoring the mark. Most students simply repeated the stem of the question and added that it was for the electricity companies to make more money. Few students realised the significance of a lower cost and the surplus of energy at night.

(c) This was poorly answered with two-thirds of students scoring zero. Many students seemed to think that the purpose of the super-efficient insulation was to completely stop any energy / heat transfer to the room. These students seem not to understand the purpose of room heaters!

(d) Nearly half of the students scored both marks. However, all students should be encouraged to copy the equation from the equation sheet and then substitute figures. If this is done correctly, students will score at least one mark. There were a significant number of errors made in transforming the equation. Students showing only an incorrect transformation gained no credit. A significant minority of students used a temperature change other than the 100 °C given.

E33. (a) (i) This was generally well-answered, although the most common mistake was to have conduction and convection the wrong way round.

(ii) Most students chose the correct answer.

(b) (i) Students coped well with this calculation, the majority obtaining the correct answer of 18.2 kWh.

(ii) This calculation however was very poorly answered. A very common answer was to write 7 x 5 = 35.

(c) The majority of Students obtained the correct answer to this calculation, although some students were unable to show the correct number of zeroes.

E34.(a) (i) Nearly all students responded correctly with ‘kinetic’ energy.

(ii) The majority of answers correctly identified the two forms of wasted energy.

(b) Just over half of responses gained credit. Insufficient responses included ‘it is wasted’ (given in the question) or ‘it turns into heat’ (answered in the previous part).

(c) (i) Fewer than half of the students gained both marks for this question, although some were able to gain one mark for calculating the cost at 40°C or 30°C.

(ii) More than half of the responses failed to gain credit, many answers indicating that the washing machine itself gave off carbon dioxide. Of those students who had the correct idea, many failed to answer the question as to why reducing the amount of energy used reduces the amount of carbon dioxide.

E35.(a) (i) Nearly all students responded correctly with ‘kinetic’ energy.

(ii) The majority of answers correctly identified the two forms of wasted energy.

(b) Just over half of responses gained credit. Insufficient responses included ‘it is wasted’ (given in the question) or ‘it turns into heat’ (answered in the previous part).

(c) (i) Fewer than half of the students gained both marks for this question, although some were able to gain one mark for calculating the cost at 40°C or 30°C.

(ii) More than half of the responses failed to gain credit, many answers indicating that the washing machine itself gave off carbon dioxide. Of those students who had the correct idea, many failed to answer the question as to why reducing the amount of energy used reduces the amount of carbon dioxide.

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· Web viewSymbol: (2) (b) When an electric current flows through a wire, the wire will get hot. ... The electricity is charged at the rate of 20 p per kWh. A £2 coin is put into