# Numerical - Max efficiency of a heat engine at a given source and sink temperature

## A cyclic heat engine operates between a source temperature of 927 0C and a sink temperature of 27 0C. What will be the maximum efficiency of the heat engine?

**Options**

a. 100 %

b. 80 %

c. 75 %

d. 70 %

Correct Answer: c. 75 %

**Explanation**

Heat engine is operated between the temperatures

T1 = 927 0C = 927 + 273 = 1200 K and

T2 = 27 0C = 27 + 273 = 300 K

The maximum efficiency of a heat engine is given by,

η_{max} = 1 – (T2/T1)

η_{max} = 1 – (300/1200)

η_{max} = 0.75