Problem 5: A heat engine operates between two reservoirs at temperatures of 25^oC and 300^oC. What is the maximum efficiency for this engine?

Solution:

Step:1 Overview

As we know that:

E=1-Q₂/Q₁

It can also be proved that heat transfered to or from a heat engine is directly proportional to temperature of hot body or cold body. Hense:

Q₂/Q₁=T₂/T₁

So the above equation becomes:

E=1-T₂/T₁

Step:2 Calculation

T₁=300^oC=537K
T₂=25^oC=298K
E=?

E=1-T₂/T₁
E=1-298K/537K
E=1-0.52
E=0.48=48% (Ans)