Four successive processes A→B, B→C, C→D and D→A constitute a cycle performed by an ideal gas. The heats absorbed (+) or rejected (–) and the work done by the system (+) or on the system (–) in the first three processes are given below.
Process Q (J) W (J)
A→B +200 +120
B→C –150 0
C→D +50 +30
D→A ? –40
(i) Find the heat exchanged in the process D→A.
(ii) Calculate the net work done by the gas in the complete cycle.
(iii) Determine the net heat absorbed over the cycle and state whether the gas, on the whole, behaves as a heat engine or as a refrigerator.