CIE iGCSE Co-Ordinated Science P2.3.2 Convection Exam Style Questions Paper 4
Question
Fig. 6.1 shows an electric refrigerator.
(a) The cooling unit inside the refrigerator is placed at the top of the refrigerator.
(i) State the name of the process which transfers most thermal energy from the food to the cooling unit inside the refrigerator.
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(ii) Explain, in terms of density changes, why the cooling unit being fitted at the top of the refrigerator allows all of the air inside to be cooled.
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(b) The refrigerator uses the compression and expansion of gases in order to transfer thermal energy to the outside of the refrigerator.
Complete Table 6.1 to show how the pressure of a fixed mass of gas changes with temperature and with volume.
(c) The cooling unit in the refrigerator uses a motor.
Fig. 6.2 shows a simple d.c. motor.
Describe two ways to make a motor turn more slowly.
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▶️Answer/Explanation
Ans: 6(a)(i) convection ;
6(a)(ii) air (at the top) is cooled and its density increases ;
the cooled air falls ;
warm(er) air has lower density and moves upwards ;
6(b)
both correct ;
6(c) any two from:
decrease the current in the coil ;
use fewer turns on the coil ;
use a weaker magnet / magnetic field ;