Q 11-11-014NEETJEE MainEAMCET 2010 (Engineering)Medium
Three moles of an ideal monatomic gas perform a cycle ABCDA. Processes AB and CD are at constant volume, and BC and DA are at constant pressure. The gas temperatures are $T_A = 400$ K, $T_B = 800$ K, $T_C = 2400$ K and $T_D = 1200$ K. The work done by the gas is approximately ($R = 8.314$ J/mol K)
Answer: (B) $20$ kJ
Concept. No work at constant volume; isobaric work $nR\Delta T$.
Step 1. Isobaric steps. $W_{BC} = 3R(1600) = 4800R$, $W_{DA} = 3R(-800) = -2400R$.
Step 2. Net. $2400R = 2400 \times 8.314 \approx 20$ kJ.
Answer. $20$ kJ (Option B).
Solution by Sreeraj P, M.Sc Physics