Question

A heat engine absorbs $760kJ$ heat from a source at $380K$. It rejects (i) $650kJ$, (ii) $560kJ$, (iii) $504kJ$ of heat to sink at $280K$. State which of these represent a reversible, an irreversible or an impossible cycle.

Answer 1

From the second law of thermodynamics, we know that

$\Delta \left(T/T^1\right)=A/Q$

A=$\Delta \ast Q/T^1=100\ast 760/380=200K$

The rejected:

$760-200=560k$

Hence $560KJ$ is reversible.