Question

For which combination of working temperatures the efficiency of Carnot's engine is highest. 

(A) 80 K, 60 K 

(B) 100 K, 80 K 

(C) 60 K, 40 K 

(D) 40 K, 20 K

Answer 1

Correct option: (D) 40 K, 20 K

Explanation:

For carnot’s engine η = 1 – (T₂ / T₁)

(a)  η = 1 – (60 / 80) = 25%

(b) η = 1 – (80 / 100) = 20% 

(c) η = 1 – (40 / 60) = 33% 

(d) η = 1 – (20 / 40) = 50%

∴ Highest efficiency in case of D.