Question

A heat engine does 30.0 J of work per cycle while exhausting 40.0 J of waste heat. Part A What is the engine's thermal efficiency? ______

Answer 1

Work done by the heat engine $=W=30J$

Waste heat $=Q_{c}=40J$

Heat input $=Q_{H}$

$Q_{H}=Q_{c}+W$

$Q_{H}=(40+30)J=70J$

$Efficiency =n=\frac{W}{Q_{H}}=\frac{30}{70}=0.4286$

Hence the efficiency is 42.86 %