Answer: 40%.
- A 20%
- B 30%
- C 40%
- D 60%
Correct answer: C. 40%
Explanation: η = 1 − T<sub>sink</sub>/T<sub>source</sub> = 1 − 300/500 = 0.4 = 40%.
The Carnot cycle alternates two isothermal steps (heat absorbed at TH, released at TC) with two adiabatic steps (no heat exchange); the enclosed loop area equals the net work output, and η = 1−TC/TH is the maximum possible efficiency between those two temperatures.
Concept context
Laws of thermodynamics, heat engines, entropy, and gas processes.