Answer: 40%.
- A 25%
- B 33%
- C 40%
- D 67%
Correct answer: C. 40%
Explanation: Q<sub>hot</sub> = W + Q<sub>cold</sub> = 1000 + 1500 = 2500 J. eta = W/Q<sub>hot</sub> = 1000/2500 = 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.