Question

A Carnot's engine can have 100% efficiency if the temperature of the sink is

• A. 273 K
• B. 0 K
• C. 0 °C
• D. 373 K

Hint:

A Carnot engine can never be 100\% efficient unless the sink is at absolute zero (0 K), which is practically impossible.

Answer 1

The Correct Option is B

Efficiency of a Carnot engine is given by $\eta = 1 - \dfrac{T_{\text{sink}}}{T_{\text{source}}}$
To get $\eta = 1$ or 100%, we must have: $\dfrac{T_{\text{sink}}}{T_{\text{source}}} = 0$ ⇒ $T_{\text{sink}} = 0$ K