UNIQUE SCIENCE ACADEMY

Transcription

1 UNIQUE SIENE AAEMY Test (Unit 1) Name :... Pap er: Physics ate :... ode: 5054 lass: I Time Allowed: 5Minutes Maximum Marks: 5 Theory Section: 1 [Total 19 Marks] 1 (a) escribe an experiment to show which of two metals is the better conductor of heat. [4] (b) Explain how heat is conducted through a metal rod. (c) Fig. 1.1 shows a solar panel that uses the Sun s energy to heat water. sunlight water out metal tube water in insulated box Fig. 1.1 The solar panel consists of a long tube of metal through which water flows. The tube is mounted in an insulated box with a glass top. oth the metal tube and the inside of the box are painted black. Explain (i) why the metal tube is mounted inside an insulated box, [1] (ii) why the metal tube is painted black. [1] [Total:8]

2 A heat pipe is a device that transmits thermal energy along its length. It can transmit energy thousands of times faster than a solid copper rod. Fig..1 shows a heat pipe attached to black metal fins. The fins absorb energy from the Sun. The sealed pipe transmits this energy along its length into a tank of cold water. tank of cold water energy from Sun black metal fins alcohol partially evacuated copper pipe sealed at both ends Fig..1 Thermal energy from the fins is conducted through the walls of the copper pipe and causes the alcohol to boil. The boiling creates a higher pressure. At the end of the copper pipe in contact with cold water, the alcohol condenses and creates a lower pressure. The liquid alcohol runs along the pipe to be boiled again. There is little change in the temperature of the alcohol. (i) escribe how molecules in the copper conduct energy to the alcohol. (ii) Explain how boiling and condensation within the heat pipe cause the transfer of energy. (iii) Explain why the heat pipe is able to transfer energy at a fast rate. [Total 6] edicated to My Son Mohammad Irtaza Zain. ode 5054

3 Fig..1 shows the plan of the dining room in a house in a cold country. etails of the rest of the rooms are not shown. The air outside the house is much colder than that inside the house. interior walls OL WARM plan (view from above) door WARM external walls dining room window (single glass) Fig..1 Heat is lost from the dining room by conduction at the rates shown below. through external walls J/hour through internal walls J/hour through door J/hour through window J/hour (a) Suggest why (i) much more heat is lost through the external walls than through the internal walls, (ii) such a lot of heat is lost through the window. (b) If the figures above relate to the only sources of heat loss, how many J/hour would the heater in the dining room need to supply in order to keep the temperature in the room constant? rate of heat supply needed =... J/hour (c) Suggest one other way heat might be lost from the room....[1] [Total;5] MQ SETION: [Total 6 Marks] 1 After the rod is heated at the join in the centre for about a minute, where would the lowest temperature be? A wood edicated to My Son Mohammad Irtaza Zain. copper ode 5054

4 4 A bar made of half wood and half copper has a piece of paper wrapped tightly round it. The bar is heated strongly at the centre for a short time, and the paper goes brown on one side only. wood paper copper heat Which side goes brown, and what does this show about wood and copper? brown side wood copper A copper conductor insulator copper insulator conductor wood conductor insulator wood insulator conductor Fibre is used for home insulation in a cold country, as shown in the diagram. roof roof space fibre ceiling 4 Heat cannot easily escape through the ceiling because the fibre A traps air. is warm. is tightly packed. heats the roof space. The diagram shows four similar cans. Each can contains the same volume of water initially at 80. After five minutes, which can will contain the warmest water? lid lid dull black polished silver dull black polished silver A

5 5 5 A student needs a double-walled glass vessel to contain a hot liquid. Q R S hot liquid space air outside glass walls What reduces heat losses by radiation? A a vacuum in the space between the walls painting surface Q black painting surface R black painting surface S silver 6 The earliest Ford cars were always painted black. This was because black paint dried more quickly than lighter colours when the cars were left in the sun to dry. Which property of black paint makes it dry more quickly? A It is the best absorber of heat. It is the best conductor of heat. It is the best insulator of heat. It is the best reflector of heat. MQ Answer Sheet 1 A 4 A A 5 A A 6 A