Question

For which combination of working temperatures, the efficiency of 'Carnot's engine is the least?

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

Answer 1

The correct option is C $100K,80K$

Efficiency of Carnot's engine $\eta =1-\frac{T_L}{T_H}$

(A) : ${\eta }_A=1-\frac{20}{40}=0.5$

(B) : ${\eta }_B=1-\frac{40}{60}=0.33$

(C) : ${\eta }_C=1-\frac{80}{100}=0.2$

(D) : ${\eta }_D=1-\frac{60}{80}=0.25$

Thus the Carnot's engine, working on the combination given in option C, has the least efficiency.