Q12.20Multiple choice
In a refrigerator one removes heat from a lower temperature and deposits to the surroundings at a higher temperature. In this process, mechanical work has to be done, which is provided by an electric motor. If the motor is of 1kW power, and heat is transferred from –3°C to 27°C, find the heat taken out of the refrigerator per second assuming its efficiency is 50% of a perfect engine. 12.21 If the co-efficient of performance of a refrigerator is 5 and operates at the room temperature (27 °C), find the temperature inside the refrigerator. 12.22 The initial state of a certain gas is (Pi, Vi, Ti). It undergoes expansion till its volume becoms Vf . Consider the following two cases:
- (a)the expansion takes place at constant temperature.
- (b)the expansion takes place at constant pressure. Plot the P-V diagram for each case. In which of the two cases, is the work done by the gas more?