A heat engine operates with 20% efficiency between two reservoirs. If T_h = 500 K, find T_c (for maximum/Carnot):
A450 K
B300 K
C400 K
D100 K
Answer & Solution
Correct answer: C. 400 K
η = 1 - T_c/T_h → 0.20 = 1 - T_c/500 → T_c/500 = 0.80 → T_c = 400 K.
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