Question

A heat engine uses thermal energy flowing from a heat source that is 225k to a cold sink that is 50k. What is the approximate efficiency of that heat engine?

Answer 1

efficiency of heat engine is given as

$\eta = 1 - \frac{T_2}{T_1}$

now we know that

$T_2$ = temperature of sink

$T_1$ = temperature of high temperature source

now it is given that

$T_2 = 50 k$

$T_1 = 225 k$

now from the given equation we have

$\eta = 1 - \frac{50}{225}$

$\eta = 0.78$

so efficiency of heat engine will be 78%