Q. Three moles of an ideal gas $\left( C_{P} = \frac{7}{2}R \right)$ at pressure $P_{A}$ and temperature $T_{A}$ is isothermally expanded to twice its initial volume. It is then compressed at constant pressure to its original volume. Finally the gas is compressed at constant volume to its original pressure $P_{A}$. The correct $P$-$V$ and $P$-$T$ diagrams indicating the process are
A)
B)
C)
D)
Explanation
(a) Let the process start from initial pressure $P_{A}$, volume $V_{A}$ and temperature $T_{A}$
(i) Isothermal expansion ($PV =$ constant) at temperature $T_{A}$ to twice the initial volume $V_{A}$
(ii) Compression at constant pressure $\frac{P_{A}}{2}$ to original volume $V_{A}(i.e.V \propto T)$
(iii) Isochoric process (at volume $V_{A}$) to initial condition $(i.e.\ P \propto T)$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.