Q. Two heat engines $A$ and $B$ have their sources at 1000 K and 1100 K and their sinks are at 500 K and 400 K respectively. What is true about their efficiencies?
A) $\eta_{A} = \eta_{B}$
B) $\eta_{A} > \eta_{B}$
C) $\eta_{A} < \eta_{B}$
D) Cannot say
Explanation
(c) $\eta_{A} = 1 - \frac{T_{2}}{T_{1}} = 1 - \frac{500}{1000} = \frac{1}{2}$
$\eta_{B} = 1 - \frac{T_{2}}{T_{1}} = 1 - \frac{400}{1100} = \frac{7}{11}$
Clearly, $\eta_{A} < \eta_{B}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.