Question

A Carnot engine can be $100\%$ efficient if its sink is at

• A. $0K$
• B. $0^{o}C$
• C. $0^{o}F$
• D. $273K$

Answer 1

The correct option is A $0K$

The carnot efficiency is given as $\eta =1-\frac{T_2}{T_1}$. Here $T_1$ is the temperature of the hot reservoir and $T_2$ is the temperature of the coldreservoir. This value of $\eta$ will be $100\%$ for $T_2=0$. As all the temperatures are in Kelvin the correct answer is $0K$.