Answer: Constant volume.
- A Constant pressure
- B Constant volume
- C Constant temperature
- D Adiabatically
Correct answer: B. Constant volume
Explanation: Otto cycle (gasoline engine): heat is added and rejected at constant volume. Compression and expansion are adiabatic.
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.