4/11.25 – Physics Help Please! Carnot Engine: got the first half, need help on second?

Question

A) A heat engine does 300J of work per cycle while exhausting 700J of heat to the cold reservoir. What is the engine's thermal efficiency? FOUND TO BE 30%

B) A Carnot engine with a hot-reservoir temperature of 430C has the same thermal efficiency. What is the cold-reservoir temperature in C?

Answer 1

B) eff = 0.3 = 1 - [Tl / Th]; Th = 430 C = 703 K (must use absolute temp scale)

Solve for Tl; I get Tl = 492 K = 219 C.

Good Luck!