Heat transfer by conduction, convection and

Transcription

1 Heat transfer by conduction, convection and radiation Question paper 2 Level Subject Exam Board Topic GCSE Physics CCEA Energy Sub-Topic Heat transfer by conduction, convection and radiation Booklet Question paper 2 Time Allowed: 60 minutes Score: /50 Percentage: /100

2 Higher Tier 1

3 1 (a) In the blank table below write the names of three renewable sources of energy and three non-renewable sources of energy. Renewable source of energy Non-renewable source of energy [3] (b) Desmond and his sleigh have a total mass of 90 kg. He does J of useful work pulling his sleigh and raising himself to the top of a snow covered hill. (i) Write down the gravitational potential energy of Desmond and his sleigh, at the top of the hill. Gravitational potential energy = J (ii) Use your answer to (i) to calculate the vertical height of the hill. You are advised to show clearly how you get your answer. Vertical height of the hill = m [4] 2

4 (iii) Desmond now sits on the sleigh and returns to the bottom of the hill. At the bottom of the hill both are moving with a speed of 15 m/s. Calculate the kinetic energy of Desmond and the sleigh. The mass of Desmond and his sleigh is 90 kg. You are advised to show clearly how you get your answer. Kinetic energy = J [3] (iv) How much energy is wasted during the descent? Energy wasted = J [2] (c) Several identical metal balls are heated until they are very hot and all at the same temperature. However, each ball is a different colour as shown below. Grey Black Silver White Yellow (i) Which ball gives out most heat radiation per second? (ii) To which part of the electromagnetic spectrum does the heat radiation belong? 3

5 One very hot ball is then placed on a glass support as shown below. Three heat sensors, A, B and C, are now positioned around the ball. Each sensor is the same distance from the ball. A C B Glass (iii) Explain fully why the reading on sensor A is highest. [2] (d) Hot takeway food is often placed in a container made of aluminium foil. The aluminium foil is shiny on both the inside and the outside surfaces. Novelis Deutschland GmbH Explain, in detail, how the container keeps the food hot. _ [2] 4

6 (e) Copper is a good conductor of heat. Glass is a poor conductor of heat. Describe, carefully, the mechanism by which heat is transferred in each of these materials, naming the particles that play an important role in the process. _ [4] Quality of written communication [2] 5

7 2 (a) The Dinorwig power station in Wales is described as a pumped storage scheme. Electricity is used to pump water into a high level lake as shown in the diagram below. This is done during the night when the demand for electricity is much lower than during the day. High Lake 70m Turbine Pump Station Low Lake Pump Station Generating facility V Ryan (i) A hydroelectric power station uses a renewable source of energy to generate electricity. What is a renewable energy source? (ii) Unlike a hydroelectric power station, the Dinorwig scheme cannot be described as a renewable energy source. Explain why. [2] 6

8 (iii) The water falls 70 m from the high lake to the turbine. Calculate the potential energy of 1 kg of water 70 m above the turbine. You are advised to show clearly how you get your answer. Potential energy J [4] Only 85% of this potential energy is converted to kinetic energy when the water falls from the high lake to the turbine. (iv) What has happened to the other 15% of the potential energy? (v) Knowing that 85% of the potential energy is converted to kinetic energy, calculate the average speed of each 1 kg of water as it reaches the turbines. You are advised to show clearly how you get your answer. Average speed m/s [5] 7

9 (vi) For every 1 kg of water that reaches the turbines 500 J of electricity are generated. Using your answer to part (iii) calculate the overall efficiency of the Dinorwig power scheme. You are advised to show clearly how you get your answer. Efficiency [3] (vii) The generators at Dinorwig can reach maximum electrical power output in 5 seconds. What advantage is this over fossil fuel or nuclear power stations? 8

10 (b) A bimetallic strip consists of two different metals. For the same increase in temperature one metal expands more than the other. The diagram below shows a bimetallic strip being used to operate an alarm should the temperature in a storeroom become too high. When the circuit is completed the alarm will sound. Alarm circuit Rivet Contact Wire Base Bimetallic strip Wire How Stuff Works (i) Describe how the bimetallic strip should behave to set the alarm off. (ii) Describe how the metals should be arranged on this bimetallic strip so that the alarm will work correctly. Remember one metal expands more than the other. 9

11 (c) The processor in a computer generates a lot of heat. This heat must be removed otherwise the processor may fail to work properly. The processor is placed in contact with a metal structure similar to the one shown below. istockphoto / Thinkstock (i) Describe how the three processes of heat transfer remove heat from the processor. [3] Quality of written communication [2] (ii) Explain why painting the metal structure black makes it more efficient at removing heat from the processor. 10