Q.Consider the following cyclic process, consisting of an isotherm, an isochoric process and an isobaric process, which is given in the figure (a closed P-V loop through three labelled states, 1, 2 and 3, taken in the order $1\to2\to3\to1$). Draw the same cyclic process qualitatively on a V-T diagram, where T is taken along the x direction and V is taken along the y direction. Analyze the nature of the heat exchange in each process.

Step 1. The cyclic process consists of an isotherm, an isochoric leg, and an isobaric leg, taken through three states 1→2→3→1 on the P-V diagram. Since the isochoric leg (2→3) and the isobaric leg (3→1) are each explicitly described by the change they involve, the remaining leg (1→2) must be the isotherm.

Step 2. Process 1→2 (isothermal): since $T$ is constant on this leg, and the process is shown as an expansion (volume increases), $\Delta U=0$, so $Q=W>0$: heat must be added, and it goes entirely into doing external expansion work.

Step 3. Process 2→3 (isochoric): volume remains constant while temperature (and pressure) increase; since $W=0$ (no volume change), the first law gives $\Delta U=Q$ -- the heat supplied is used entirely to increase the internal energy (and hence the temperature).

Step 4. Process 3→1 (isobaric): pressure remains constant while both volume and temperature are reduced back to the starting state; this is an isobaric COMPRESSION, so work is done ON the system ($W<0$), and heat flows OUT of the system ($Q<0$) as it is compressed and cooled. …

Identify the isochoric and isobaric legs first (as explicitly named in the two remaining constraints), leaving the third leg as the isotherm by elimination; …

• Assuming heat is added throughout the whole cycle -- it is added on TWO legs (1→2 and 2→3) but flows OUT on the third (3→1), consistent with the cycl …