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Name: _______________________________________________
Energy stores & transfer
Date:
Time: Total marks available: Total marks achieved: ______
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Questions
Q1(a) A student investigates the energy transfers in a small generator.She connects the generator to a circuit that includes a lamp.She hangs a mass from a string wound around the axle.The lamp lights as the mass falls to the ground.
The table shows the student's results.
(i) State the equation linking gravitational potential energy, mass, g and height.
(1)
(ii) Calculate the gravitational potential energy, GPE, lost by the mass.(2)
GPE = ...........................................................J
(iii) Explain why only some of the gravitational potential energy of the mass is transferred to the lamp.(2)
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(iv) Calculate the energy transferred to the lamp.(2)
energy transferred = ...........................................................J
(b) Water from a reservoir can be used to generate electricity on a large scale.
Describe the energy transfers involved in this process.(3)
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(Total for question = 10 marks)Q2.The diagram shows the percentages of thermal energy lost from a house.
(a) The house loses a total amount of 1.2 × 107 J of thermal energy each day.
Calculate the amount of thermal energy lost through the walls in one week.(3)
(b) State how to reduce the amount of thermal energy lost through the windows.
(1)
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(c) The roof could be insulated with fibreglass wool, which contains lots of trapped air.
Explain how this insulation reduces the amount of thermal energy lost from the roof.(4)
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(d) The house is heated with a gas boiler that is 75% efficient.
Chemical energy in the gas is transferred to thermal energy by burning.Some of the thermal energy is useful.Some of the thermal energy is wasted.Draw a Sankey diagram for this energy transfer.
(3)
(Total for question = 11 marks)
Q3.The diagram shows an electric kettle.
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(a) The Sankey diagram shows the energy transfers that take place in one second when the kettle heats some water.
What is the energy input in one second?(1)
A 250 J B 2000 J C 2250 J D 2500 J
(b) There is a large insulated coil of wire inside the kettle.
Explain why this coil of wire gets hot when the kettle is switched on.(2)
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..................................................................................................................................................................................... (c) The power of the kettle is 2.5 kW when operating at a voltage of 230 V.
(i) State the equation linking power, current and voltage.(1)
(ii) Show that the current in the kettle is about 11 A.(2)
(iii) The plug of the kettle is fitted with a 13A fuse.Describe how the fuse prevents the coil of wire from overheating.
(3)
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(Total for question = 9 marks)
Q4.The diagram shows some electrical appliances.
(a) (i) Which appliance is designed to transfer electrical energy to thermal energy? (1)
A food mixer B kettle C lamp D radio
(ii) Which appliance is designed to transfer electrical energy to kinetic energy?(1)
A food mixer B kettle C lamp D radio
(b) In all the appliances, energy is conserved.
What is meant by the phrase energy is conserved?(1)
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.................................................................................................................................................................................... (c) (i) The lamp has an efficiency of 20%.Explain what this means.
(2)
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(ii) Draw a labelled Sankey diagram for the lamp.(3)
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(Total for question = 8 marks)Q5.The photograph shows equipment used for generating electricity from renewable sources.
(a) Complete the sentences using words from the box.
(i) The panel of solar cells transforms ............................................................................................. energy into electrical energy.
(1)(ii) The wind turbine transforms .................................................................................energy into (1)electrical energy.
(b) On a windy day, the wind turbine transfers 78 W of power.(i) State the equation linking power, energy transferred and time. (1)
(ii) Calculate the amount of energy the turbine transfers in 10 s.(3)
Energy transferred = ........................................................... J(c) The Sankey diagram shows the energy transferred by the panel of solar cells.
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Show that the efficiency of the panel of solar cells is 12%.(2)
(Total for question = 8 marks)Q6.A shopping centre has escalators to move people between floors.
(a) A man of mass 78 kg steps on to an escalator.The escalator lifts him a height of 5.0 m.(i) State the equation linking gravitational potential energy, mass, g and height. (1)
(ii) Show that the gravitational potential energy gained by the man is about 4000 J.(2)
(iii) State the work done on the man and give the unit.
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(2)
Work done = ........................................................... Unit ...........................................................(b) The escalator is powered by a 7.5 kW electric motor.
(i) State the equation linking efficiency, useful energy output and total energy input.(1)
(ii) The escalator lifts 30 people each minute.Each person has a mass of 78 kg.
Calculate the efficiency of the escalator.(3)
Efficiency = ...........................................................(c) Another escalator has an efficiency of 20%.Its input power is 15 kW.
Draw a Sankey diagram for this escalator.(3)
(Total for question = 12 marks)Q7.The photograph shows a child bouncing on a trampoline.
(a) The box lists some types of energy.Page 9 of 12
The passage describes the process of bouncing on the trampoline.Use words from the box to complete the passage.Each word may be used once, more than once or not at all.
(4)As the child falls, his ..................................................................energy is mostly transferred to
....................................................energy.When the child hits the trampoline, his ..........................................energy
is transferred to ...........................................energy. (2)
Q8.A girl slides from point A to point B on a plastic slide.
(a) State the main type of energy lost as the girl travels from A to B.
(1)
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Q9.The photograph shows a solar-powered battery charger connected to a mobile phone.
When the battery charger is used, it transfers light energy from the Sun to the battery of the mobile phone.Page 10 of 12
(a) Complete the energy transfer diagram.(2)
Q10.A golfer hits a golf ball and it bounces into the hole.
(a) Use words from the box to complete the sentences below.Each word may be used once, more than once, or not at all.
(i) Each time the golf ball moves upwards, it gains .........................................................................potential energy.
(1)(ii) Each time the golf ball hits the ground it changes shape and energy is stored as ..............................................potential energy. (1)(iii) When the golf ball is moving it has ......................................................................... energy.(1)(b) Each time the ball hits the ground, energy is transferred away from the ball.
(i) How can you tell this from the diagram?(1)
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(ii) Describe what happens to the energy that is transferred.(1)
................................................................................................................................................................. .........................................................................................................................................................................(Total for question = 5 marks)Q11.(a) The box lists some devices that can be used to transfer energy from one form into another.
Select a device from the box to complete each sentence.(2)
Sound energy is changed into electrical energy using ............................................................
Electrical energy is changed into sound energy using ............................................................
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