Problem 10.12 (Zemansky) A body of finite mass is originally at a temperature , which is higher than that of a reservoir at the temperature . Suppose an engine operates in a cycle between the body and the reservoir until it lowers the temperature of the body from to , thus extracting heat Q from the body. If the engine does work W, then it will reject heat Q-W to the reservoir at . Applying the entropy principle, we have to prove that the maximum work obtainable from the engine is
where is the entropy decrease of the body.
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Solution: Click For PDF Version The entropy principle is that the change of entropy of the universe as a result of any kind of process is greater than or equal to zero. That is
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