2.3 Convection Marks : _____________ Date : ______________

Section A: True or False 1 In order to reduce the temperature of a room, we should install an

air conditioner at a lower position.

(1)

2 In order to increase the temperature of a room, we should install an

electric heater at a lower position.

(2)

Section B: Fill in the blanks 1 Convection is the transfer of heat by the movement (1) of -(1)-. It takes place only in -(2)- and gases. (2) 2 In convection, the hot fluid (liquids or gases) -(3)- (3) and becomes less -(4)-. It rises upwards together (4) with heat. 3 The cold fluid sinks to the bottom to replace the hot fluid. As a result, a -(5)- current is produced. (5) 4 Heat is transferred in liquids by the movement of -(6)- from one place to another. This kind of heat (6) transfer is called –(7)-, which always produces (7) a convection –(8)-. (8) 5 In convection, hot molecules always move –(9)-. (9) Section C: Multiple Choice Questions 1 Why should the cooling part of the refrigerator be placed at the

upper position?

A Because it is more convenient to use. B Because warm air is at the bottom of the refrigerator. C Because cold air sinks to cool the whole refrigerator. D Because ice can be formed more easily in the upper part of

the refrigerator.

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2 In the figure below, where should an air conditioner be placed so

that it can work more effectively?

A A B B C C D D

3 Which of the following statements about convection is correct? A Hot molecules move slower than cooler ones. B Hot molecules do not move but pass energy to their

neighbours.

C Hot molecules move together with their energies. D Hot molecules emit their energies in all direction. 4 Which of the following statements is/are correct? (1) Conduction is the transfer of heat from objects with higher

internal energy to objects with lower internal energy.

(2) During convection, hot air rises because it possess higher internal energy than cool air.

(3) Internal energy is a measure of the extent of molecular motions and interactions.

A (2) only B (3) only C (1) and (2) only D (1) and (3) only 5 Air conditioners are usually installed high on the wall to make use of

the effect of heat transfer by

A Conduction B Convection C Radiation D flowing of air

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Section D: Structured Questions 1 Describe briefly how convection currents are formed in fluids. Ans: 2 Describe the method of convection. Ans:

End

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