JEE Main 2026 · 6 Apr · Shift 1, Physics question 50

Key's working. The work is taken as the bulk modulus times the volume change:
$$W=B\,\Delta V=3\times10^5\times(3-1)\times10^{-3}=600\text{ J}.$$

Note. For an isothermal ideal gas $B=P$, so B changes during the compression. Integrating $\int P\,dV$ with $P_0=B=3\times10^5$ Pa at the start would give $P_0V_0\ln3\approx989$ J. The official answer is 600.

Answer: 600