Answer: Always increases or stays constant.
- A Always decreases toward a minimum equilibrium value
- B Stays exactly constant for every real spontaneous process
- C Always increases or stays constant
- D Fluctuates randomly with no preferred direction over time
Correct answer: C. Always increases or stays constant
Explanation: Second law: entropy of an isolated system always increases or stays constant. Spontaneous processes increase total entropy.
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.