Question

A heat engine absorbs 760 kJ 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 and an impossible cycles.

Answer 1

Solution: 
According to 2d law of Thermodynamics:
delta(T/T1) = A/Q
A = deltaT *Q / T1 = 100 * 760 / 380 = 200 kJ. 
Rejected: 760 – 200 = 560 kJ – ii (reversible cycle).
Hence (ii) 560 kJ - reversible cycle.