Answer: 2000 K.
- A 1600 K
- B 2000 K
- C 3200 K
- D 800 K
Correct answer: B. 2000 K
Explanation: eta = 1 - T<sub>c</sub>/T<sub>h</sub>. 0.8 = 1 - 400/T<sub>h</sub>. 400/T<sub>h</sub> = 0.2. T<sub>h</sub> = 2000 K.
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.