Question

The temperature of source and sink of a heat engine are ${127}^o$C and ${27}^o$C, respectively. An inventor claims its efficiency of be $26\%$, then.

• A. It is impossible
• B. It is possible with high probability
• C. It is possible with low probability
• D. Data are insufficient

Answer 1

The correct option is A It is impossible

Efficiency of heat engine is $\eta =1-\frac{T_2}{T_1}$ or $\eta =\frac{T_1-T_2}{T_1}$
Here, $T_1=273+127=400$K
$T_2=273+27=300$K
$\therefore \eta =\frac{400-300}{400}=\frac{100}{400}=0.25=25\%$.
Hence, $26\%$ efficient is impossible for a given heat engine.