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

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1 1 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 (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 Energy transferred each day =... kwh Page 1 of 19

2 (iii) Energy costs 15 p per kilowatt-hour. Calculate the cost of heating the house for one day.... Cost =... (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 Page 2 of 19

3 (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 The plastic foam reduces energy transfer by convection. Explain why. (Total 8 marks) Page 3 of 19

4 2 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 Page 4 of 19

5 (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. (Total 5 marks) Page 5 of 19

6 3 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. Page 6 of 19

7 (b) Use the equation in the box to calculate the efficiency of the electric motor. Show clearly how you work out your answer. Efficiency =... (Total 3 marks) 4 Electrical appliances transfer energy in different ways. Figure 1 shows a television. Figure 1 (a) Use the correct answer from the box to complete the sentence. less than more than the same as Energy is conserved by the television. Energy is conserved, means that the energy input is... the total energy output. Page 7 of 19

8 (b) The power input to the television is 120 W. Calculate the total energy transferred by the television when it is switched on for 300 seconds. Use the correct equation from the Physics Equations Sheet. Energy =... J (c) Figure 2 shows a torch that does not need batteries. Figure 2 Shaking the torch up and down for 5 minutes generates enough electricity to light the torch bulb for 20 minutes. Use the correct answer from the box to complete each sentence about the energy transfers. elastic potential kinetic light sound When the torch is shaken up and down, the torch transfers... energy to electrical energy. When the torch is turned on, the bulb usefully transfers electrical energy to... energy. (Total 5 marks) Page 8 of 19

9 5 (a) The diagram shows a solar powered device being used to recharge a mobile phone. On average, the solar cells produce 0.6 joules of electrical energy each second. The solar cells have an efficiency of (i) Calculate the average energy input each second to the device. Show clearly how you work out your answer Average energy input each second =... J/s (ii) Draw a labelled Sankey diagram for the solar cells. The diagram does not need to be drawn to scale. (b) Scientists have developed a new type of solar cell with an efficiency of over 40 %. The efficiency of the solar cell was confirmed independently by other scientists. Suggest why it was important to confirm the efficiency independently. Page 9 of 19

10 (c) The electricity used in homes in the UK is normally generated in a fossil fuel power station. Outline some of the advantages of using solar cells to generate this electricity. (Total 6 marks) Page 10 of 19

11 6 (a) A student investigated the insulating properties of three materials. The diagram shows the apparatus the student used. In the investigation: different insulating materials, A, B and C, were placed in contact with the hot metal plate temperature sensors measured the temperature on each side of the material the difference in temperature across the insulating material was then calculated the differences in temperature were compared to measure the effectiveness of each insulating material. The graph shows how the temperature measured by temperature sensor 2 changed over 10 minutes for each of the materials. (i) What was the temperature of the hot metal plate?... C Page 11 of 19

12 (ii) Which material, A, B or C, is the best insulator? Material:... Give a reason for your answer (b) The table shows information about three home insulation methods for an average sized home. Insulation method Cost of insulation in Savings per year in Double glazing Draught excluders Loft insulation Which method of home insulation is the most cost-effective over 10 years? You must include calculations in your answer (4) (Total 7 marks) Page 12 of 19

13 7 A householder wants to reduce her electricity bills. The householder takes readings from her electricity meter to see how much electricity she is using. The pictures show the electricity meter readings at the start and end of April in At the start of April At the end of April (a) How many kilowatt-hours of electricity did she use in April? Number of kilowatt-hours =... Page 13 of 19

14 (b) The householder wants to reduce energy transfer from a room so she puts a special sheet between a heater and the wall. The side of the sheet facing the heater is shiny metal foil. The side of the sheet facing the wall is polystyrene. The polystyrene contains bubbles of trapped air. What properties of the sheet make it good for reducing energy transfer from the room? Draw a ring around each correct answer to complete the sentences. absorbers (i) Shiny surfaces are good emitters of infrared radiation. reflectors conductor. (ii) The air in the polystyrene is a good insulator. emitter. Page 14 of 19

15 (c) The householder turns her heater thermostat down by 2 C so the temperature of the room is lower. The specific heat capacity of air is 1000 J/kg C. The mass of air in the room is 50 kg. Calculate the energy needed to change the temperature of 50 kg of air by 2 C. Use the correct equation from the Physics Equations Sheet. Energy =... J (Total 6 marks) Page 15 of 19

16 8 The picture shows a temporary road traffic information board. The batteries power the LEDs used in the information board. The solar cells keep the batteries charged. (a) Use words from the box to complete each of the following sentences. chemical electrical light sound The solar cells transfer light energy to... energy. The batteries transfer... energy to electrical energy. The LEDs transfer electrical energy to... energy. (3) (b) When the total energy input to the solar cells is 200 joules, the useful energy output from the solar cells to the batteries is 50 joules. Calculate the efficiency of the solar cells. Efficiency =... Page 16 of 19

17 (c) Which one of the following statements gives the reason for using solar cells to charge the batteries? Tick ( ) one box. Solar cells will charge the batteries day and night. The information board can be used anywhere it is needed. A small number of solar cells produce a lot of electricity. (Total 6 marks) 9 A student finds some information about energy-saving light bulbs. (a) A 30W light bulb uses 600J of electrical energy in a certain period of time. In that time, it produces 450 J of light energy. The rest of the energy is wasted. (i) Calculate the energy wasted by the light bulb in this period of time. Wasted energy =... J (ii) What happens to the energy wasted by the light bulb? (iii) Calculate the efficiency of this light bulb. Efficiency =... Page 17 of 19

18 (iv) Calculate the period of time, in seconds, during which the 600 J is provided to the 30 W light bulb. Time =... s (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 LED bulb (i) Suggest why it is important to confirm this information independently. (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. (iii) State one factor, other than efficiency, that is important when considering the choice of a bulb for lighting in the home. (Total 10 marks) Page 18 of 19

19 10 The diagram shows what happens to each 100 joules of energy from crude oil when it is used as petrol in a car. The widths of the arrows show exactly how much energy is transferred in each particular way. (a) (b) Complete the diagram by adding the correct energy value alongside each arrow. Calculate how efficient the car engine is at transferring the energy from petrol into useful movement. Show clearly how you work out your answer. (Total 4 marks) Page 19 of 19