All Carnot engines have zero efficiency if they are operating between two bodies with
Correct answer: C. The same temperature irrespective of the nature of working substance.
- A. The same temperature and the same nature of working substance.
- B. Different temperature and the same nature of working substance.
- C. The same temperature irrespective of the nature of working substance.
- D. Different temperatures irrespective of the nature of working substance.
Explanation
The efficiency of a Carnot engine is determined by the temperature difference between the hot and cold reservoirs. If the temperatures are the same, there is no temperature gradient to drive the engine, resulting in zero efficiency. Therefore, the correct answer is that all Carnot engines have zero efficiency if they are operating between two bodies with the same temperature, irrespective of the nature of the working substance. The other options suggest scenarios where there is either a temperature difference or an irrelevant factor (the nature of the working substance) affecting efficiency.
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About Thermal Equilibrium and Heat
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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