JEE MAIN - Physics (2022 - 28th June Evening Shift - No. 8)
A sample of an ideal gas is taken through the cyclic process ABCA as shown in figure. It absorbs, 40 J of heat during the part AB, no heat during BC and rejects 60 J of heat during CA. A work of 50 J is done on the gas during the part BC. The internal energy of the gas at A is 1560 J. The workdone by the gas during the part CA is :
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20 J
30 J
$$-$$30 J
$$-$$60 J
Explanation
$$\Delta$$UAB = 40 J as process is isochoric.
$$\Delta$$UBC = + 50 (WBC = $$-$$ 50 J)
UC = UA + $$\Delta$$UAB + $$\Delta$$UBC = 1650
For CA process,
QCA = $$-$$ 60 J
$$\Delta$$UCA + WCA = $$-$$60
$$-$$90 + WCA = $$-$$ 60
$$\Rightarrow$$ WCA = +30 J
The graph given is inconsistent with the statement BC may be adiabatic and CA cannot be like isobaric as shown, as increasing volume while rejecting heat at same time.
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