UNIQUE SCIENCE ACADEMY

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1 UNIQUE SIENE EMY Test (Unit 11-12) Name :... Paper: Physics ate :... ode: 5054 lass: II Time llowed: 35Minutes This document consists of 5 printed pages. Maximum Marks: 25 T [Total 21 Marks] heory Section: 1 This question is about thermal () energy. The diagram shows a method of ing a room using solar energy instead of conventional sources of energy. brick wall with a blackened surface is placed behind a double-glazed window facing the Sun. uring the day the wall stores energy received from the Sun as energy. 1 Room eiling Gap rick wall ouble-glazed window lackened surface Floor Gap (a) (i) Name the only method by which energy from the Sun is transferred to the Earth. Give a reason for your answer. (ii) Why is the surface of the wall blackened?

2 (iii) Name the method by which energy from the blackened surface is transferred to the air next to it. [1] (iv) escribe how this ed air is transferred throughout the room. [3] (v) The double-glazed window consists of two sheets of glass which trap a layer of air between them. Explain how using a double-glazed window increases the rate at which the temperature of the room rises. [Total 10] 2 person running in a race generates, on average, 800 J of energy every second. Half of this energy is lost from the body by the evaporation of. (a) Explain, in terms of molecules, how the loss of by evaporation cools the body (b) alculate the mass of evaporated from the body in a 2 hour race. The specific latent of vaporisation of is J/kg. mass = [3] [Total 5]

3 3 n electric soldering iron is used to melt solder, for joining wires in an electric circuit. soldering iron is shown in Fig copper tip metal cylinder with er coil inside plastic handle lead to electricity supply Fig. 3.1 Solder is a metal which melts easily. The er coil inside the metal cylinder s the copper tip. (a) (i) Suggest why the tip is made of copper. (ii) Suggest why the handle is made of plastic. (b) The er coil is switched on. When the tip is put in contact with the solder, some of the is used to melt the solder. (i) State the process by which the is transferred from the copper tip to the solder. (ii) y which process or processes is the rest of the transferred to the surroundings? Tick the boxes alongside any of the following (you may tick as many as you think are correct). conduction convection evaporation radiation (c) short time after switching on the soldering iron, it reaches a steady temperature, even though the er coil is constantly generating. The soldering iron is rated at 40 W. What is the rate at which is being lost from the soldering iron? Tick one box. greater than 40 W equal to 40 W less than 40 W [1] [Total 6]

4 1 MQ SETION: [Total 4 Marks] The diagrams show part of a -ing system which is working by convection. Which diagram shows the most likely flow of in the system? 4 2 The diagram shows a er used to a of cold. lagging er What is the main process by which moves through the? conduction convection evaporation radiation

5 5 3 The diagram shows a block of copper placed in a cold room. t which point is the temperature the highest? clamp copper table 4 n iron bar is held with one end in a fire. The other end soon becomes too to hold. hand iron bar fire How has the travelled along the iron bar? by conduction by convection by expansion by radiation MQ nswer Sheet