Question

For which combination of working temperatures is the efficiency of carnot engine highest ?

• A. 80 K, 60 K
• B. 100 K, 80 K
• C. 60 K, 40 K
• D. 40 K, 20 K

Answer 1

Answer: (D)

40 K, 20 K

Efficiency of Carnot's cycle is
$\eta =1-\frac{T_C}{T_H}$
i)$\eta =1-\frac{60}{80}=0.25$
ii)$\eta =1-\frac{80}{100}=0.2$
iii)$\eta =1-\frac{40}{60}=0.33$
iv)$\eta =1-\frac{20}{40}=0.5$
Option D.