JEE Main · 2020 · 09 Jan 2020 · Shift 1 · Heat & Thermodynamics

Follow the three legs of the cycle. The adiabatic expansion $1\to 2$ lowers both pressure and temperature along a curve. The leg $2\to 3$ is isothermal, so on a $P$ versus $T$ plot it is a vertical line at fixed $T$ while the pressure changes. The leg $3\to 1$ is isobaric, a horizontal line at fixed $P$ while the temperature changes. The faithful $P$ versus $T$ picture is thus the one that shows a sloping curve for the adiabatic $1\to 2$, a vertical segment for the isothermal $2\to 3$, and a horizontal segment for the isobaric $3\to 1$.