Q 11-11-012NEETJEE MainEAMCET 2014 (Engineering)Easy
The volume of one mole of a gas is changed from $V$ to $2V$ at constant pressure $p$. If $\gamma$ is the ratio of specific heats of the gas, the change in internal energy of the gas is
Answer: (D) $\dfrac{pV}{\gamma - 1}$
Concept. $\Delta U = \dfrac{nR\Delta T}{\gamma - 1}$, and at constant pressure $nR\Delta T = p\Delta V$.
Step 1. Substitute.
$$\Delta U = \frac{p(2V - V)}{\gamma - 1} = \frac{pV}{\gamma - 1}$$
Answer. $\dfrac{pV}{\gamma - 1}$ (Option D).
Solution by Sreeraj P, M.Sc Physics