A heat engine operates with a hot reservoir at 500 K and a cold reservoir at 300 K. If 1000 J of heat is absorbed, the maximum work output is:
Correct answer: A. 400 J
- A. 400 J
- B. 600 J
- C. 300 J
- D. 1000 J
Explanation
The maximum efficiency of a Carnot engine is η = 1 - (Tcold/Thot) = 1 - (300/500) = 0.4. Maximum work output is η × Qhot = 0.4 × 1000 = 400 J.
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Thermal equilibrium means that bodies in contact have the same temperature and no net heat flows between them. The topic distinguishes heat from temperature, uses the zeroth law of thermodynamics, and covers heat transfer, specific heat capacity, thermal expansion and the conditions for reaching equilibrium.
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