Question

2. For a heat engine shown below, the low temperature in the cycle increases from 275 to 285 K, while other temperatures (including the low temperature reservoir) and QH stay the same. What happens to the entropy change of the low-temperature reservoir? Explain for full credit hot reservoirTh500 K 1250. ー S,--2.50 JIK A. decreases QH1250. J B. increases TH 500 K C. does not change 0.43 Ws-538.J Tc 285K AStotal 0.09 J/K Qc -713. J ASc 2.59 J/K cold rese

Answer 1

The answer is (C) - does not change

The hot and cold reservoir temperature are maintained the same at 500 K and 275 K, even after temperature increase to 285 K, of the low temperature cycle.

Reason:

Entropy is a state function and is a property of the system. The change in property of the system is a state function and depends only on the initial and final state and is independent of the path followed.

That is irrespective of whether a system follows a reversible or irreversible path, the change in entropy of the system is the same for fixed initial and final state.

In our case, the hot and cold reservoir temperature are maintained the same at 500 K and 275 K and hence the entropy change is the same before and after cycle temperature increase for the reasons stated above.