For isothermal $AB$: $Q_{AB} = nRT\ln 2$ (heat absorbed)
For isochoric $BC$: volume constant, pressure and temperature decrease
For isobaric $CA$: compression back to initial state
$$\eta = 1 - \frac{\ln 2}{2\ln 2 - 1}$$
Back to JEE Main 2022 Thermodynamics
JEE Main 2022 — Physics Thermodynamics
hard
mcq
2022
Official previous-year question
Verified 30 May 2026.
Question
An ideal gas undergoes a cyclic process $ABCA$ where $AB$ is isothermal expansion at $T = 400\,\text{K}$ from volume $V$ to $2V$, $BC$ is isochoric cooling, and $CA$ is isobaric compression. The efficiency of the cycle is:
Options
- A
$1 - \frac{\ln 2}{2\ln 2 - 1}$
- B
$1 - \frac{1}{1 + \ln 2}$
- C
$1 - \frac{1}{2\ln 2}$
- D
$\frac{\ln 2}{1 + \ln 2}$
Solution
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