€¦ · Web viewSolar Cooker. Specific Heat ... many candidates opted for kinetic or electrical energy.A few candidates read the word ‘as’ to mean ‘because’ and wrote a

Colonel Frank Seely 2014

Exam Question Unit 1 Practice (Maths Focus)

Q Description Skill Focus Max Score

Lower Challenge

1 Electricity Bill Calculate KWhours 4

2 Stair Lift Efficiency Calc 3

3 Solar Aircraft Efficiency Calc 5

4 SHC BlockReading from Graph/ Describe a graph trend/

Calc Power/ Payback Time11

5 Solar Cooker Specific Heat Capacity (E = ?) 6

6 Refraction Anomalous Data id on graph 8

Medium Challenge

7 Washing Machine Reading from graph & KW hour calc 7

8 House Insulation Power Calc/ KW hour / U Value 11

9 Freezer Costs KW hour calcs/ Payback 6

10Electricity

Demand GraphQWC – Comparing costs of production 9

11Comparing Power

StationsSankey - efficiency 7

12 Lifting a LoadReading from a Graph / Estimating Costs from

KW hour8

Higher Challenge

13 Low Energy BulbsComparing a CFL and LED from table /

Power / Efficiency8

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14Energy

ConservationComparing Bills from a table 5

15 Radio Beacons calculation 4

16 Energy Sources Advantages/Disadvantages from costs table 6

17 Solar EnergyInterpreting data on Month/Tilt Angle from a

table & efficiency linked calculation10

18 EM Wavelengths calculation 6

Extension Questions (A*)

19 Sankey - LEDWasted energy / time calcs / data table cost

comparison Filament to LED bulb10

20 EM SpectrumStandard form / freq calc / X-Ray Doses from

table12

Progress Checker (shade in your score)1 1 2 3 42 1 2 33 1 2 3 4 54 1 2 3 4 5 6 7 8 9 10 115 1 2 3 4 5 66 1 2 3 4 5 6 7 87 1 2 3 4 5 6 78 1 2 3 4 5 6 7 8 9 10 119 1 2 3 4 5 6

10 1 2 3 4 5 6 7 8 911 1 2 3 4 5 6 712 1 2 3 4 5 6 7 813 1 2 3 4 5 6 7 814 1 2 3 4 515 1 2 3 416 1 2 3 4 5 617 1 2 3 4 5 6 7 8 9 1018 1 2 3 4 5 6

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19 1 2 3 4 5 6 7 8 9 1020 1 2 3 4 5 6 7 8 9 10 11 12

Lower Challenge Section Q1-6Q1.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 x 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 53782.

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

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

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

(Total 4 marks)

Q2. A person uses a stairlift to go upstairs. The stairlift is powered by an electric motor. The Sankey diagram shows the energy transfers for the electric motor.

(a) Complete the following sentence.

The electric motor wastes energy as .............................................. energy.(1)

Q3.The picture shows a solar-powered aircraft. The aircraft has no pilot.

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By NASA/Nick Galante [Public domain], via Wikimedia Commons

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

electrical heat light sound

Solar cells are designed to transform ............................................................. energy

into ............................................................. energy.(2)

(b) On a summer day, 175 000 joules of energy are supplied to the aircraft’s solar cells every second. The useful energy transferred by the solar cells is 35 000 joules every second.

Use the equation in the box to calculate the efficiency of the solar cells.


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

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

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

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(c) The aircraft propellers are driven by electric motors.

Give one environmental advantage of using electric motors to drive the aircraft propellers rather than motors that burn a fuel.

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

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

(Total 5 marks)

Q4.(a) A student used the apparatus drawn below to investigate the heating effect of an electric heater.

(i) Before starting the experiment, the student drew Graph A.

Graph A shows how the student expected the temperature of the metal block to change after the heater was switched on.

Describe the pattern shown in Graph A.

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

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

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

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

(ii) The student measured the room temperature. He then switched the heater on and measured the temperature of the metal block every 50 seconds.

The student calculated the increase in temperature of the metal block and plottedGraph B.

After 300 seconds, Graph B shows the increase in temperature of the metal block is lower than the increase in temperature expected from Graph A.

Suggest one reason why.

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

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

(iii) The power of the electric heater is 50 watts.

Calculate the energy transferred to the heater from the electricity supply in 300 seconds.

Use the correct equation from the Physics Equations Sheet.

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

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

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

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

(b) The student uses the same heater to heat blocks of different metals. Each time the heater is switched on for 300 seconds.

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Each block of metal has the same mass but a different specific heat capacity.

Metal Specific heat capacity in J/kg°C

Aluminium 900

Iron 450

Lead 130

Which one of the metals will heat up the most?

Draw a ring around the correct answer.

aluminium iron lead

Give, in terms of the amount of energy needed to heat the metal blocks, a reason for your answer.

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

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

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

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

(c) A homeowner uses an electric immersion heater to heat the water in his hot water tank. The hot water tank has no insulation.

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(i) Draw a ring around the correct answer to complete each sentence.

conduction.

Energy is transferred through the water by convection.

evaporation.

conduction.

Energy is transferred through the copper wall of the hot water tank by convection.

evaporation.

(2)

(ii) To keep the water in the tank hot for longer, the homeowner fits an insulating jacket around the tank. The insulating jacket costs £12 to buy.

The homeowner expects to save £16 each year from reduced energy bills.

Calculate the pay-back time for the insulating jacket.

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

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

Pay-back time = ........................................... years(2)

(Total 11 marks)

Q5.The diagram shows the design of a solar cooker. The cooker heats water using infrared radiation from the Sun.

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(a) Why is the inside of the large curved dish covered with shiny metal foil?

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

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

(b) Which would be the best colour to paint the outside of the metal cooking pot?

Draw a ring around the correct answer.

black silver white

Give a reason for your answer.

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

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

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

(c) Why does the cooking pot have a lid?

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

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

(d) Calculate how much energy is needed to increase the temperature of 2 kg of water by 80 °C.

The specific heat capacity of water = 4200 J/kg °C.


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

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

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

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

(Total 6 marks)

Q6.A student investigated the refraction of light as it passed out of a clear plastic block into the air.

Diagram 1 shows the apparatus the student used.

Diagram 1

(a) The angle i is the angle of incidence.

Use the letter r to mark the angle of refraction on Diagram 1.(1)

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(b) The student measured the angle of refraction for different angles of incidence. The results are shown in the graph.

Angle of incidence in degrees

(i) One of the results seems to be anomalous.

Draw a ring around the anomalous data point on the graph.(1)

(ii) The student did measure the angles of incidence accurately.

What is likely to have caused the anomalous result?

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

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

(iii) What conclusion can the student make from the results shown in the graph?

Draw a ring around the correct answer to complete each sentence.

less than

The angle of refraction equal to the angle of incidence.

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is

greater than

(1)

(c) Light travelling from water into air is refracted in the same way as when light travels from plastic into air.

Diagram 2 shows a large bottle, filled with water. The bottle is made from clear plastic.

Draw on Diagram 2 the path of the light ray as it passes out of the bottle into the air.

Diagram 2

(2)

(d) In some countries, people are too poor to pay for electricity. Some people living in small houses with no natural light use bottles filled with water as a sort of light bulb.

The bottles are fitted into small holes in the roof of the house. Sunlight goes into the bottle of water. When the light leaves the bottle, the light is refracted, causing sunlight to spread into the room.

Diagram 3

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(i) What is likely to be the most important outcome of using this simple device to provide light?

Tick ( ) one box.

People will have enough light to work inside their homes.

Fewer plastic bottles will be thrown into rubbish tips.

Plastic bottles will increase in value.

(1)

(ii) Suggest one disadvantage of using this device compared with using a light bulb.

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

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

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

(Total 8 marks)

Medium Challenge Section Q7-12

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Q7.The picture shows a 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 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.

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Temperature setting in °C

(i) Electricity costs 15p 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.

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)

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Q8.Diagram 1 shows the energy transferred per second from a badly insulated house on a cold day in winter.

Diagram 1

(a) (i) When the inside of the house is at a constant temperature, the energy transferred from the heating system to the inside of the house equals the energy transferred from the house to the outside.

Calculate, in kilowatts, the power of the heating system used to keep the inside of the house in Diagram 1 at a constant temperature.

1 kilowatt (kW) = 1 kilojoule per second (kJ/s)

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

Power of the heating system = ...................................................... kW(1)

(ii) In the winter, the heating system is switched on for a total of 7 hours each day.

Calculate, in kilowatt-hours, the energy transferred each day from the heating system to the inside of the house.


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

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

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

(iii) Energy costs 15 p per kilowatt-hour.

Calculate the cost of heating the house for one day.

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

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

(iv) The heating system is switched off at midnight.

The graph shows how the temperature inside the house changes after the heating system has been switched off.

Time of day

Draw a ring around the correct answer in the box to complete the sentence.

Between midnight and 6 am the rate of energy transfer from

decreases.

the house decreases then stays constant.

increases.

Give the reason for your answer.

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

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

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(b) Diagram 2 shows how the walls of the house are constructed.Diagram 3 shows how the insulation of the house could be improved by filling the air gap between the two brick walls with plastic foam.

Diagram 2 Diagram 3

U-value of the wall = 0.7 U-value of the wall = 0.3

(i) The plastic foam reduces energy transfer by convection.

Explain why.

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

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

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

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

(ii) Filling the air gap with plastic foam reduces the U-value of the wall.

What is meant by the term U-value?

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

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

(c) A homeowner has part of the outside wall of her house removed and replaced with double-glazed glass doors.

U-value of the wall = 0.3

U-value of glass doors = 1.8

Explain the effect of replacing part of the outside wall with glass doors on the rate of

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energy transfer from the house.

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

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

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

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

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

(Total 11 marks)

Q9. 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.

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

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.

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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

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Q10.(a) The graph shows how the demand for electricity in the UK changes during one 24-hour period.

Time of day

The table gives the start-up times for two types of power station.

Type of power station Start-up time

Gas A few minutes

Nuclear Several days

How would these two types of power station be used to meet the demand for electricity during this 24-hour period?

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

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

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

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

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

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Q10 (b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.

A farmer plans to generate all the electricity needed on her farm, using either a biogas generator or a small wind turbine.

The biogas generator would burn methane gas. The methane gas would come from rotting the animal waste produced on the farm. When burnt, methane produces carbon dioxide.

The biogas generator would cost £18 000 to buy and install. The wind turbine would cost £25 000 to buy and install.

The average power output from the wind turbine would be the same as the continuous output from the biogas generator.

Evaluate the advantages and disadvantages of the two methods of generating electricity.

Conclude, with a reason, which system would be better for the farmer to buy and install.

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

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

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

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

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

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

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

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

........................................................................................................................(6)

(Total 9 marks)

Q11.The Sankey diagrams show the energy transfers in a traditional coal-burning power station and a combined heat and power (CHP) station.

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Waste energyWaste energy

(a) What effect does the waste energy from a power station have on the surroundings?

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

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

(b) Calculate the efficiency of the CHP station.


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

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

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

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

(c) Why is a CHP station more efficient than a traditional coal-burning power station?

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

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

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

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

(d) A CHP station is usually used to meet the demand for electricity within the local area. The electricity is not transmitted and distributed through the National Grid.

(i) What is the National Grid?

Tick ( ) one box.

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A system of cables and pylons.

A system of cables and transformers.

A system of cables, transformers and power stations

(1)

(ii) Using the electricity locally and not transmitting it through the National Grid increases the overall efficiency of a CHP station by 7%.

Give one reason why.

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

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

(Total 7 marks)

Q12. 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)

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(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)

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(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.



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

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

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

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

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

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

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

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

(Total 8 marks)

Higher Challenge Section Q13-18

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Q13. 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)

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Q13 (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)

Q14. The table gives information about some methods of conserving energy in a house.

Conservation method Installation costin £

Annual saving onenergy bills in £

Cavity wall insulation 500 60

Hot water tank jacket 10 15

Loft insulation 110 60

Thermostatic radiator valves

75 20

(a) Explain which of the methods in the table is the most cost effective way of saving energy over a 10 year period. To obtain full marks you must support your answer with calculations.

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

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

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

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

(b) Describe what happens to the energy which is 'wasted' in a house.

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

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

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

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

(Total 5 marks)

Q15. In the diagram below A and B are two radio navigation beacons. They both transmit at 1.5 MHz. The waves from both A and B have the same amplitude and they are in phase with each other. A ship is at point X, 1600 m away from each beacon.

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(i) Calculate the wavelength of the radio waves.(The speed of radio waves is 3 × 108 m/s.)

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

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

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

(ii) Calculate the number of wavelengths which is equal to the distance between A and X.

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

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

(Total 4 marks)

Q16. Use of renewable sources of energy is expected to increase. The table shows the comparative costs of producing I kWh of electricity from different energy sources.

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Types of energy sources usedin the UK

Cost of producing 1 kWh ofelectrical energy

Fossil fuels (non-renewable) Coal 1.0 p

Gas 1.4 p

Oil 1.5 p

Nuclear fuels (non-renewable)

Nuclear 0.9 p

Renewable Hydroelectric 0.2 p

Wind 0.9 p

Installation and decommissioning costs are not included

At present about 2% of electricity generated in the UK uses renewable energy sources. Consider the three types of energy sources in the table and give one advantage and one disadvantage for each (other than installation and decommissioning costs).

Advantage Disadvantage

Using fossil fuels

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

.

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

.

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

.

Using fossil fuels

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

.

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

.

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

.

Using nuclear fuels

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

.

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

.

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

.

Using nuclear fuels

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

.

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

.

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

.

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Using renewable sources

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

.

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

.

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

.

Using renewable sources

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

.

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

.

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

.

(Total 6 marks)

Q17.(a) Solar energy is a renewable energy source used to generate electricity.

(i) What is meant by an energy source being renewable?

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

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

(ii) Name two other renewable energy sources used to generate electricity.

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

2 ...............................................................................................................(1)

(b) A householder uses panels of solar cells to generate electricity for his home.The solar cells are tilted to receive the maximum energy input from the Sun.

The data in the table gives the average energy input each second (in J/s), to a 1 m2 area of solar cells for different angles of tilt and different months of the year.

Month

Angle of tilt

20° 30° 40° 50°

February 460 500 480 440

April 600 620 610 600

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June 710 720 680 640

August 640 660 640 580

October 480 520 500 460

December 400 440 420 410

(i) Use the data in the table to describe how the average energy input to the solar cells depends on the angle of tilt.

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

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

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

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

(ii) The total area of the solar cell panels used by the householder is 5 m2.

The efficiency of the solar cells is 0.18.

Use the equation in the box to calculate the average maximum electrical energy available from the solar cell panels each second in June.


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

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

Maximum energy = ............................................... joules/second(3)

(c) The diagram shows part of the National Grid.

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(i) Even though the householder uses solar cells to generate electricity for his home, the home stays connected to the National Grid.

Give one reason why the householder should stay connected to the National Grid.

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

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

(ii) The step-up transformer increases the efficiency of the National Grid.

Explain how.

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

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

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

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

(Total 10 marks)

Q18.(a) The wavelengths of four different types of electromagnetic wave, including visible light waves, are given in the table.

Type of wave Wavelength

Visible light 0.0005 mm

A 1.1 km

B 100 mm

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C 0.18 mm

Which of the waves, A, B, or C, is an infra red wave?

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

(b) A TV station broadcasts at 500 000 kHz. The waves travel through the air at 300 000 000 m/s.

Use the equation in the box to calculate the wavelength of the waves broadcast by this station.

wave speed = frequency x wavelength


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

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

Wavelength = ............................................... m(2)

(c) What happens when a metal aerial absorbs radio waves?

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

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

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

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

(d) Stars emit all types of electromagnetic waves. Telescopes that monitor X-rays are mounted on satellites in space.

Why would an X-ray telescope based on Earth not be able to detect X-rays emitted from distant stars?

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

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

(Total 6 marks)

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Extension Section Q19/20

Q19.A student finds some information about energy-saving light bulbs.

(a) The Sankey diagram is for a 30 W light bulb over a period of time.

(i) Calculate the energy wasted by the light bulb in this period of time.

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

Wasted energy = ................................. J(1)

(ii) What happens to the energy wasted by the light bulb?

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

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

(iii) Calculate the efficiency of this light bulb.

Use the correct equation from Section C of the Physics Equations Sheet.

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

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

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

(iv) Calculate the period of time, in seconds, during which the 600 J is provided to the 30 W light bulb.

Use the correct equation from Section C of the Physics Equations Sheet.

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

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

Time = ......................... s(2)

(b) A company that makes light bulbs provides information about some of their products.

The table shows some of this information.

Power in watts Lifetime in hours Cost of bulb in £

Filament bulb 60 1250 2.00

LED bulb 12 50 000 16.00

(i) Suggest why it is important to confirm this information independently.

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

(ii) A homeowner is thinking about replacing his filament bulbs with LED bulbs.

A 12 W LED bulb gives the same light output as a 60 W filament bulb.

Suggest reasons why the homeowner is likely to choose LED bulbs.

Use the information given in the table.

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

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

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

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

(iii) State one factor, other than efficiency, that is important when considering the choice of a bulb for lighting in the home.

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

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

(Total 10 marks)

Q20.Different parts of the electromagnetic spectrum have different uses.

(a) The diagram shows the electromagnetic spectrum.

Radio waves Microwaves Infrared Visible

light Ultraviolet X-rays

Gamma rays

(i) Use the correct answers from the box to complete the sentence.

amplitude frequency speed wavelength

The arrow in the diagram is in the direction of increasing .........................

and decreasing ........................ .(2)

(ii) Draw a ring around the correct answer to complete the sentence.

The range of wavelengths for waves in the electromagnetic

spectrum is approximately

10-15 to 104

10-4 to 104

104 to 1015

metres.

(1)

(b) The wavelength of a radio wave is 1500 m.The speed of radio waves is 3.0 × 108 m / s.

Calculate the frequency of the radio wave.

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Use the correct equation from Section B of the Physics Equations Sheet.

Give the unit.

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

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

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

Frequency = ........................................Hz(2)

(c) (i) State one hazard of exposure to infrared radiation.

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

(ii) State one hazard of exposure to ultraviolet radiation.

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

(d) X-rays are used in hospitals for computed tomography (CT) scans.

(i) State one other medical use for X-rays.

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

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

(ii) State a property of X-rays that makes them suitable for your answer in part (d)(i).

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

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

(iii) The scientific unit of measurement used to measure the dose received from radiations, such as X-rays or background radiation, is the millisievert (mSv).

The table shows the X-ray dose resulting from CT scans of various parts of the body.

The table also shows the time it would take to get the same dose from background radiation.

Part of thebody

X-ray dosein

Time it would take to get the samedose from background

Mr Powell 2014 40


mSv radiation

Abdomen 9.0 3 years

Sinuses 0.5 2 months

Spine 4.0 16 months

A student suggests that the X-ray dose and the time it would take to get the same dose from background radiation are directly proportional.

Use calculations to test this suggestion and state your conclusion.

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

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

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

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

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

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

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

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

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

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

(Total 13 marks)

Mr Powell 2014 41


M1.(a) £16.50allow 1 mark for correct substitution ie 110 × 15an answer of 1650 gains both marksan answer of 43.80 gains both marksallow 1 mark for 292 × 15

2

(b) 292allow 1 mark for correctly using the reading 53490 ie 53782 – 53490accept £43.80 for both marks

2[4]

M2. (a) heat / thermalor / andsounddo not accept noiseother forms of energy eg light negates answer

1

(b) 0.4or40 %

allow 1 mark for orequivalent fractionan answer 0.4 % gains 1 markanswers 0.4 or 40 given with any unit gains 1 mark40 without % gains 1 mark

2[3]

M3.(a) lightcorrect order only

1

electrical1

(b) 0.2 or 1/5accept 20% for both marks

Mr Powell 2014 42


allow 1 mark for correct substitution ie answers of 0.2% or 20 gain 1 mark only

2

(c) any one from:

• produces no (pollutant) gasesorno greenhouse gasesaccept named gasaccept no air pollution do not accept no pollutionaccept less global warmingaccept harmful for pollutantaccept produces no carbon do not accept environmentally friendly

• produces no / less noise

• less demand for fuelsaccept any other sensible environmental advantage

1[5]

M4.(a) (i) temperature (increase) and time switched on are directly proportionalaccept the idea of equal increases in time giving equal increases in temperatureanswers such as:• as time increases, temperature increases• positive correlation• linear relationship• temperature and time are proportionalscore 1 mark

2

(ii) any one from:“it” refers to the metal block

• energy transfer (from the block) to the surroundingsaccept lost for transferaccept air for surroundings

• (some) energy used to warm the heater / thermometer (itself)accept takes time for heater to warm up

• (metal) block is not insulated1

(iii) 15 000allow 1 mark for correct substitution, ie 50 × 300 provided no

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subsequent step shown2

(b) leadreason only scores if lead is chosen

1

needs least energy to raise temperature by 1°Caccept needs less energy to heat it (by the same amount) lowest specific heat capacity is insufficient

1

(c) (i) convectioncorrect order only

1

conduction1

(ii) 3 / 4 (year)

or

allow 1 mark for correct method, ie shown

0.75

or

9 months

or

274 days2

[11]

M5.(a) to reflect (the infrared)accept (shiny surfaces) are good reflectorsignore reference to incorrect type of wave

1

(b) black1

best absorber (of infrared)answer should be comparativeblack absorbs (infrared) is insufficientaccept good absorber (of infrared)ignore reference to emitter

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ignore attracts heatignore reference to conduction

1

(c) to reduce energy lossaccept to stop energy loss accept heat for energy accept to stop / reduce convection

orso temperature of water increases fasteraccept to heat water faster accept cooks food faster

orreduces loss of water (by evaporation)1

(d) 672 000allow 1 mark for correct substitution, ie 2 × 4200 × 80 provided no subsequent step shown

2[6]

M6.(a) angle of refraction correctly identifiedaccept any correct indication

1

(b) (i) result at i = 25° identified1

(ii) measuring angle of refraction incorrectlyaccept any practical suggestion that would lead to the angle r being incorrecteg placing the protractor in the wrong placenot marking the refracted ray correctly / accurately / ray box has been moveddo not accept measured angle i and angle r incorrectlydo not accept plotted incorrectly

1

(iii) greater than1

(c) shown refracting out of the bottle with angle of refraction larger than angle of incidence

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allow 1 mark for refraction shown on correct side of normal with angle of refraction smaller than angle of incidence

2

(d) (i) People will have enough light to work inside their homes1

(ii) accept any sensible suggestiondo not accept roof leaks

eg does not work at nightno control over light cannot switch on and off

eg cannot control brightness1

[8]

M7.(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

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

orbecomes dissipated / spread out

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

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(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

• fewer power stations needed

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

2[7]

M8.(a) (i) 5(.0)1

(ii) 35 or their (a)(i) × 7 correctly calculatedallow 1 mark for correct substitution, ie 5 or their (a)(i) × 7 provided no subsequent step shown

2

(iii) 525(p)or(£) 5.25ortheir (a)(ii) × 15 correctly calculated

if unit p or £ given they must be consistent with the numerical answer

1

(iv) decreases1

temperature difference (between inside and outside) decreasesaccept gradient (of line) decreasesdo not accept temperature (inside) decreasesdo not accept graph goes down

1

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(b) (i) air (bubbles are) trapped (in the foam)do not accept air traps heat foam has air pockets is insufficient

1

(and so the) air cannot circulate / move / form convection currentair is a good insulator is insufficient no convection current is insufficientanswers in terms of warm air from the room being trapped are incorrect and score no marks

1

(ii) how effective / good a material is as an insulator / at keeping energy inaccept heat for energy accept the lower the U-value the better the insulator accept the lower the U-value the lower the rate of energy / heat transfer

1

(c) it will increaseroom will be cooler is insufficient

1

because the glass is not (such) a good insulator (as the wall)the U-value has increased is insufficient

1[11]

M9. (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 / used

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accept 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]

M10.(a) any three from:

• gas can be switched on (and off) quickly but nuclear cannotgas has a short start-up time alone is insufficient

• gas can be used to meet surges in demandaccept specific times from graph, anything from 1700 to 2200

• gas can contribute to / meet the base load

• nuclear provides base loadornuclear is used to generate all of the time

3

(b) Marks awarded for this answer will be determined by the Quality of Written Communication (QWC) as well as the standard of the scientific response. Examiners should also refer to the information in the Marking guidance, and apply a ‘best-fit’ approach to the marking.

0 marksNo relevant content.

Level 1 (1-2 marks)There is a brief description of one advantage or disadvantage of using either biogas or windormakes a conclusion with a reason.

Mr Powell 2014 49


Level 2 (3-4 marks)There is a description of some advantages and / or disadvantages for biogasand / or windorthere is a direct comparison between the two systems and at least one advantage / disadvantageora detailed evaluation of one system only with a conclusion.

Level 3 (5-6 marks)There is a clear and detailed comparison of the two systems.

There must be a clear conclusion of which system would be best with at least one comparative reason given for the choice made.

Examples of the points made in the responseextra information

Biogas

• renewable

• energy resource is free

• reliable energy sourceaccept works all of the time

• does not depend on the weather

• uses up (animal) waste products

• concentrated energy source

• cheaper (to buy and install)accept once only

• shorter payback-time (than wind)

• adds carbon dioxide to the atmospherewhen waste burns it produces carbon dioxide is insufficient

• contributes to the greenhouse effectorcontributes to global warming

• no transport cost for fuels

Wind turbine

• renewable

• energy resource is free

• not reliable

• depends on the weather / wind

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• will be times when not enough electricity generated for the farm’s needs

• dilute energy source

• longer payback-time (than biogas)

• more expensive (to buy and install)accept once only

• does not produce any carbon dioxideaccept does not pollute airaccept pollutant gases for carbon dioxideproduces visual or noise pollution is insufficient harmful gases is insufficient

6[9]

M11.(a) warms itdo not accept answers in terms of waste gases or pollution

1

(b) 80% or 0.8answers of 80 or 0.8 plus a unit gain 1 mark only

or allow 1 mark for a correct substitution, ie an answer of 35% or 0.35 gains 1 markanswers of 85%, 75%, 0.85 or0.75 gain 1 mark

2

(c) some of the energy that would be wasted (by a coal-burning power station)accept less waste energy

1

is usefully used (to heat homes etc)accept energy used to heat homes etc

1

(d) (i) A system of cables and transformers1

(ii) less energy / power loss / wasted (in shorter cables)accept no energy / power loss / wasted (in shorter cables)accept energy is lost when transmitted through cablesdo not accept electricity for energy

1[7]

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M12. (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 rapidlysimply 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

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less greenhouse gas (produced)saves energy is insufficient

1[8]

M13. (a) (i)

1.6 (W)

allow 1 mark for correct substitution ie 2

(ii)

32 (%) / 0.32ortheir (a)(i) ÷ 5 correctly calculatedignore any units

1

(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

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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]

M14. (a) loft insulation1

energy saved in 10 years £6001

net saving (600 – 110) £4901

OR

hot water jacket1

energy saved in 10 years £1401

This is the highest percentage saving on cost1

(b) transferred to environment / surroundings

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1

as heat / thermal energy1

[5]

M15. (i) Speed = wavelength × frequency3.108 = 1.5.106 × wavelengthWavelength = 200mfor 1 mark each

3

(ii) 81

[4]

M16. do not give any credit for renewable or non-renewable or installation or decommissioning costs

fossil fuel advantage1

a reliable source of energy

fossil fuel disadvantage

pollution by carbon dioxide /accept causes acid rainaccept highest costs / more expensive than nuclear / more expensive than renewable

1

nuclear advantage

do not produce gases that increase thegreenhouse effect or cause acid rain

accept nuclear is cheaper than fossil1

nuclear disadvantage

accidents / waste can release very dangerous radioactive material radiationaccept it produces waste that stays dangerously radioactive for thousands of years or radioactive waste has to be stored safely for

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thousands of years1

renewable advantage

there are no fuel costsalmost pollution free (apart from noise and visual)accept cheaper than fossil

1

renewable disadvantage

not a reliable source of energy except for hydroelectricaccept (most) require large areas of landaccept visual / noise pollution

1[6]

M17.(a) (i) replaced faster than it is usedaccept replaced as quick as it is usedaccept it will never run out do not accept can be used again

1

(ii) any two from:two sources required for the mark

• wind

• waves

• tides• fall of water

do not accept water / oceansaccept hydroelectric

• biofuelaccept a named biofuel eg wood

• geothermal1

(b) (i) any two from:

• increases from 20° to 30°

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• reaches maximum value at 30°

• then decreases from 30°

• same pattern for each monthaccept peaks at 30° for both marksaccept goes up then down for 1 mark ignore it’s always the lowest at 50°

2

(ii) 648an answer of 129.6 gains 2 marksallow 1 mark for using 720 value only from table allow 2 marks for answers 639, 612, 576, 618(.75) allow 1 mark for answers 127.8, 122.4, 115.2, 123.75

3

(c) (i) (sometimes) electricity demand may be greater than supply (of electricity from the system)

accept cloudy weather, night time affects supply

or

can sell (excess) electricity (to the National Grid)1

(ii) decreases the currentaccept increases the voltage

1

reducing energy loss (along cables)accept less heat / thermal energy lost / produced

1[10]

M18.(a) C or 0.18 mm1

(b) 0.6 (m)allow 1 mark for correct substitution and/or transformation or 1mark for changing frequency to Hz answer 600 gains 1 mark

2

(c) creates an alternating currentaccept ‘ac’ for alternating currentaccept alternating voltage

1

with the same frequency as the radio wave

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accept signal for radio waveaccept it gets hotter for 1 mark provided no other marks scored

1

(d) X-rays cannot penetrate the atmosphereaccept atmosphere stops X-raysdo not accept atmosphere in the way

or

X-rays are absorbed (by the atmosphere) before reaching Earthignore explanations

1[6]

M19.(a) (i) 1501

(ii) transferred to the surroundings by heatingreference to sound negates mark

1

(iii) 0.75450 / 600 gains 1 markaccept 75% for 2 marksmaximum of 1 mark awarded if a unit is given

2

(iv) 20 (s)correct answer with or without working gains 2 markscorrect substitution of 600 / 30 gains 1 mark

2

(b) (i) to avoid bias1

(ii) use less power and last longer1

1 LED costs £16, 40 filament bulbs cost £80

or

filament costs (5 times) more in energy consumption1

(iii) any one from:

• availability of bulbs• colour output

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• temperature of bulb surface1

[10]

M20.(a) (i) frequency1

wavelength1

(ii) 10-15 to 104

1

(b) 2.0 × 105

correct substitution of3.0 × 108 / 1500 gains 1 mark

2

(c) (i) (skin) burns1

(ii) skin cancer / blindness1

(d) (i) any one from:

• (detecting) bone fractures• (detecting) dental problems• treating cancer

1

(ii) any one from:

• affect photographic film• absorbed by bone• transmitted by soft tissue• kill (cancer) cells

answer must link to answer given in (d)(i)1

(iii) 9 / 36 = 0.250.5 / 2 = 0.254 / 16 = 0.25

accept:36 / 9 = 42 / 0.5 = 416 / 4 = 4

2

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conclusion based on calculationtwo calculations correct with a valid conclusion scores 2 marksone correct calculation of k scores 1 mark

1[13]

E1.(a) Generally this was well done, with most students realising that 110 kWh should be multiplied by 15. Some students lost credit for use of units inconsistent with their numerical answers.

(b) This question was surprisingly badly done and appeared to indicate that the students had not read the information given carefully enough. Instead of simply subtracting the 'previous reading' of 53 490 kWh from the 'new reading' of 53 782, many responses attempted complicated and difficult calculations using the data provided.

E2. (a) Just under a half of the candidates wrote a correct response of either heat (thermal) or sound energy as the form of wasted energy. However, many candidates opted for kinetic or electrical energy.A few candidates read the word ‘as’ to mean ‘because’ and wrote a sentence in the gap to try to explain why energy is wasted.

(b) There was a pleasing response to this question, with about half of the candidates obtaining the correct answer to the calculation. The most common mistake was to invert the fraction and hence arrive at an answer of 2.5 rather than 0.4.

E3.(a) A majority of students were able to answer this question correctly. Nearly every response indicated that the student realised that the end product of this energy transformation would be 'electrical', but some thought that it was the Sun's 'heat' that was transformed.

(b) A good proportion managed the calculation and scored both marks. A minority used the data the wrong way round and got '5' as the efficiency. Some students were penalised for missing the percentage sign when it was appropriate or for adding spurious units to their answer.

(c) Many students realised that using electric motors meant no release of polluting or harmful gases into the atmosphere. However, it must be emphasised again that vague terms like 'environmentally friendly' or 'eco friendly' will not gain any credit. A small proportion of answers indicated that some thought electric motors were powered by wind energy rather than solar.

E4.(a) (i) Although most students could describe the pattern as being linear, very few referred to the fact that the graph showed direct proportionality.

(ii) There were very few correct answers to this question. A few suggested it took time for the heater to warm up but other acceptable answers were rarely seen. Many

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stated that the difference was because the first graph was a “guess” and the second was a “real” result. There was a lot of discussion about the original room temperature and some thought that since the student was reading the temperature every 50s, they had to switch off the heater whilst they were doing this.

(iii) The majority of students could correctly complete the calculation to find the energy transferred.

(b) The majority of students chose aluminium rather than lead, presumably because it had the highest specific heat capacity. Of those who did select lead, very few were able to provide an adequate reason.

(c) (i) Most students were able to score both marks in this question.

(ii) There were few correct answers to this question. The most common method was to multiply the two numbers and thereby end up with a figure of 192 years for the pay-back time.

E5.(a) Most students realised that a shiny surface would be a good reflector, but many used the word “bounce” instead of “reflect”. The most common wrong response was to say that metals are good conductors.

(b) Although most students correctly chose black as the best colour to paint the outside of the metal cooking pot, there was much confusion as to the reason. Many students stated that black was the best colour to attract the Sun. Some students stated that black would absorb energy without making any comparison, e.g. by stating that black is a good absorber. As in previous papers there was much confusion between absorption and emission.

(c) The great majority of students could give a correct reason for having a lid: usually to keep the heat in or to stop the water evaporating.

(d) The majority of students could correctly complete the calculation. Some however, although they could correctly substitute the numbers into the appropriate equation, were unable to calculate the correct value. This may have been either because they did not have a calculator or they were unable to use the calculator correctly. Some students incorrectly chose to convert the mass in kilograms into grams before doing the calculation.

The correct numerical answer was 672000. Some students sensibly wrote this as 672,000 using a comma as a separator. Others wrote it as 672’000 using an apostrophe as a separator.

E6.(a) Fewer than half of the students could correctly identify the angle of refraction. The most common mistake was to label the angle between the refracted ray and the plastic block. Some students chose to label a ray rather than an angle.

(b) (i) The great majority of students correctly identified the anomalous point. Of those who failed to score a mark the usual reason was because they had circled the point plotted at 30° as well as the point at 25°.

(ii) Only about a quarter of the students were able to suggest a sensible reason for the anomalous result, usually related to the block or the ray box having moved. There

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were many cases where this question was not attempted.

(iii) Most students chose the correct response that the angle of refraction is greater than the angle of incidence.

(c) Half of the students failed to score any marks on this question. Many students showed internal reflection rather than refraction. Of those who did show refraction, a large proportion showed the emergent ray on the wrong side of the normal.

(d) (i) About half of the students chose the correct answer that people will have enough light to work inside their homes. The other half mainly chose the incorrect answer that fewer plastic bottles will be thrown into rubbish tips.

(ii) Most students realised that there would be no light at night using this system. A few were concerned about the holes in the roof. Others thought that evaporation of water from the bottle would be a problem.

E7.(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.

E8.(a) (i) Many students left this part blank. Around half of the students obtained the correct answer of 5 (kW) and they were often able to go on and obtain both marks in part (ii).

(ii) Many students left this part blank.

(iii) Many students left this part blank. This part caused more difficulty with students commonly multiplying the cost per kWh by the days or by 24. Those failing to calculate part (i) correctly often went on to gain credit with the error carried forward into the other two parts although for part (iii), correct answers for part (ii) were sometimes ignored for another quantity. Perhaps this was due to the students not recognising how the parts were connected.

(iv) Whilst many students scored the first mark for saying that the rate of energy transfer from the house decreases, only a handful gained the second. Most simply stated the temperature dropped over the time period in question. A sizeable minority chose the second option for the first marking point, saying that between 5.30 and 6.00 am the graph did not change.

(b) (i) Most students found this difficult. “Hot air being trapped in the cavity” or “heat being

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trapped in the air bubbles” were common incorrect responses. Many simply repeated that energy transfer by convection would be reduced, which they were told in the stem of the question.

(ii) Many students were not able to give an indication that they understood the idea of U-value. Often they simply tried to substitute a word for U e.g. “ultimate value” or “ultra value”. Others were influenced by the word 'value' and related it to economics in some way.

(c) A major misconception of many students is that double-glazing is the best form of thermal insulation. Therefore many answered with statements like 'the rate would fall because glass is such a good insulator'. Others thought that 'heat would be trapped by the vacuum between the panes of glass'. Yet others obviously did not understand the term 'energy transfer'.

E9. (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.

E10.(a) Two thirds of the students failed to score any marks on this question. Many students failed to gain marks due to the idea that this was the first day of generating electricity and nuclear needed a long start-up time so gas would be used until nuclear was ready. This misconception gave students little chance to gain any credit. Those who did score credit usually recognised the idea that gas could be turned on quickly and / or could be used to supply at peak demands. Many students thought that the gas power station provided gas to the home.

(b) Nearly all students attempted this question and most got some credit, usually for comparing the costs of the two methods. Many students gave vague statements where the science was weak and incomplete. Some of these students were the more able who wrote eloquently but failed to gain credit because of phrases such as “eco-friendly”, “environmentally friendly” or made statements which did not go far enough such as “cause pollution”, “harmful”. Many students wrote about visual pollution, noise, harming birds, smells on the farm, etc. In the future, they need to elaborate ideas, giving more exact details. Most students made a choice and gave sensible reasons for that choice. The more able students were able to compare the advantages and disadvantages of both systems, and provide an overall conclusion at the end. Many students simply listed advantages and

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disadvantages of the two methods and did not attempt to fully answer the question by making a clear conclusion – as the question asked. Some students thought that the animal waste was dead animals or animals that need to be killed as the energy source. Other misconceptions included methane being non-renewable, the production of carbon dioxide being an advantage (helping the farmer's plants grow better) and that the major disadvantage of biogas was the smell. It was pleasing to see that more students were planning their answer before starting it.

E11.(a) Very few students appreciated that the waste energy from the power station would cause an increase in temperature of the surroundings. Of those who were thinking along these lines they often stated that the waste energy from the power station would cause global warming. Many students thought that the waste would be in the form of gases and were therefore talking about pollution of the environment.

(b) The best students were able to correctly calculate the efficiency of the CHP station. However, some of these failed to gain maximum marks because either they neglected to insert the % sign after the number 80 or they quoted the efficiency as 0.8 but then put a % sign or a unit after the number.

(c) About half of the students gained one of the two marks on this question.

(d) (i) Very few students knew that the National Grid comprises cables and transformers; the majority thought that it comprised cables and pylons.

(ii) Few students could provide an adequate reason for the increased efficiency. Responses such as “the electricity doesn't have to travel far”, “it's quicker/cheaper” and the use of “electricity” rather than “energy” meant that many scored no marks.

E12. (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’.

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E13. (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’.

E14. (a) This part was well answered. Most candidates were able to identify loft insulation as the most effective method and provided calculations supporting this conclusion.

(b) A surprising number made no reference to heat/thermal energy in their responses.

E16. Several marks could have been obtained by using comparative costs from the table but most candidates ignored it or gave only partially correct answers such as, ‘renewable is cheaper than nuclear’. References to environmental effects were usually on the level of ‘it is cleaner / dangerous’, rather than referring to specific pollutants such as carbon dioxide, sulphur dioxide and radioactive waste.

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E17.(a) (i) Around half of the responses scored the mark for this question. A common errors was to indicate that the energy source could be used again.

(ii) Three-quarters of students gave two correct responses.

(b) (i) Students found difficulty in analysing the data to find any patterns. Around half were able to identify that an angle of 30° led to the maximum average energy input. A large number of students saw the word ‘average’ and attempted to calculate the average of the values given for each month. A surprisingly high number of responses seemed to think that the ‘degrees’ referred to the temperature.

(ii) A minority of students gained all three marks for this calculation, but more were able to gain one mark by correctly identifying the value of 720 J/s.

(c) (i) Around two-thirds of students were able to give a coherent and correct answer.

(ii) Less than one-fifth of responses gained both marks, slightly more students were able to gain one mark, usually for indicating that less energy would be lost. ‘Absolute’ statements such as ‘no energy would be lost’ were often seen.

E18.(a) Generally this was well done, with most students realising that 110 kWh should be multiplied by 15. Some students lost credit for use of inconsistent units with their numerical answers.

(b) A minority of students gained both marks for this question. Half of students were able to score one mark for working out an answer of 600 m, having failed to convert the frequency from kHz to Hz.

(c) Despite this answer being a direct fact as given in the specification, the majority of students failed to gain any credit.

(d) Less than a quarter of students scored this mark. A common answer was to say that the stars emitting X-rays were too far away.

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Documents

€¦ · Web viewSolar Cooker. Specific Heat ... many candidates opted for kinetic or electrical energy.A few candidates read the word ‘as’ to mean ‘because’ and wrote a