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JEE Advanced 2025Physics Thermodynamics

hard
mcq
2025
Official previous-year question

Verified 30 May 2026.

Question

For an ideal gas undergoing an adiabatic process where $PV^{\gamma} = \text{const}$ and $\gamma = \frac{5}{3}$, the work done when volume changes from $V_1$ to $2V_1$ is:

Options

  1. A

    $\frac{P_1 V_1 \left(1 - 2^{-2/3}\right)}{\frac{2}{3}}$

  2. B

    $\frac{3P_1 V_1}{2}\left(1 - 2^{-2/3}\right)$

  3. C

    $P_1 V_1 \ln 2$

  4. D

    $\frac{2P_1 V_1}{\gamma - 1}$

Solution

For an adiabatic process: $PV^{\gamma} = P_1 V_1^{\gamma} = \text{const}$

$$W = \int_{V_1}^{2V_1} P \, dV = P_1 V_1^{\gamma} \int_{V_1}^{2V_1} V^{-\gamma} \, dV$$

$$= P_1 V_1^{\gamma} \cdot \frac{V^{1-\gamma}}{1-\gamma}\Bigg|_{V_1}^{2V_1}$$

$$= \frac{P_1 V_1}{\gamma - 1}\left(1 - 2^{1-\gamma}\right) = \frac{3P_1 V_1}{2}\left(1 - 2^{-2/3}\right)$$

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