An ideal gas is taken reversibly from state i, at temperature T₁, to any of the other states labelled, I, II, III, IV and V on the p-V diagram below. All are at the same temperature T₂. Rank the five processes according to the change in entropy of the gas, least to greatest :

Question

G1 Physics · Accepted Answer

Use the first law Q=ΔU+W (W by the gas), ΔU=nCᵥΔT for an ideal gas, and the appropriate process relation. For Carnot devices, let T₁ be the cold-reservoir temperature and T₂ be the hot-reservoir temperature; η=1-T₁/T₂ and COP=T₁/(T₂-T₁). Evaluating the given data/statements gives A: I, II, III, IV, V. Therefore the correct answer is A.