JEE Advanced · 2006 · 09 Apr 2006 · Heat & Thermodynamics

Analyzing each process from the P-V diagram:

(A) JK: Compression at constant temperature (isothermal). Work is done on the gas ($\Delta W<0$), and since $\Delta U=0$ for isothermal process, $\Delta Q<0$. Matches (Q).

(B) KL: Expansion (volume increases). Work is done by the gas ($\Delta W>0$). Temperature increases, so $\Delta U>0$, and $\Delta Q>0$. Matches (P) and (S).

(C) LM: Expansion continues. Work done by gas ($\Delta W>0$), heat added ($\Delta Q>0$). Matches (S).

(D) MJ: Compression (volume decreases). Work done on gas ($\Delta W<0$), heat released ($\Delta Q<0$). Matches (Q) and (R).

Pairs: (A)→(Q), (B)→(P),(S), (C)→(S), (D)→(Q),(R)