The second law of thermodynamics implies that
Correct answer: B. no heat engine can convert all the heat it takes in into work
- A. energy can be created in a heat engine
- B. no heat engine can convert all the heat it takes in into work
- C. heat always flows from cold to hot on its own
- D. entropy always decreases
Explanation
Some heat must always be rejected to a cold reservoir, so efficiency is necessarily less than 100 per cent however well the engine is built. Heat flows spontaneously from hot to cold, never the reverse without work being done, which is the other common statement of the same law. The entropy of an isolated system increases or at best stays constant.
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About First Law of Thermodynamics
The first law relates heat supplied, work done and the change in internal energy through energy conservation. Problems use sign conventions and apply the law to isothermal, adiabatic, isobaric and isochoric processes. Internal energy is a state function, while heat and work depend on the path followed.
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