Two engines A and B have source temperatures 400 K and 350 K, and sink temperatures 350 K and 300 K, respectively. Let η₁ and η₂ be the efficiencies of engines A and B. Which result is correct?
Options

Question

Two engines A and B have source temperatures 400 K and 350 K, and sink temperatures 350 K and 300 K, respectively. Let η₁ and η₂ be the efficiencies of engines A and B. Which result is correct?

G1 Physics · Accepted Answer

For a Carnot engine, η=1−T₁/T₂, where T₁ is the cold-reservoir temperature and T₂ is the hot-reservoir temperature. Thus η₁=1−350/400=12.5% and η₂=1−300/350≈14.3%. Engine B is more efficient. Option A.