Question

In Carnot engine efficiency is 40% , when the temperature of hot reservoir is T. For efficiency 50%, what will be temperature of hot reservoir?

• A. $\frac{T}{5}$
• B. $\frac{2T}{5}$
• C. $6T$
• D. $\frac{6T}{5}$

Answer 1

The correct option is D $\frac{6T}{5}$

Efficiency, $\eta =1-\frac{T_c}{T_h}$

For, $\eta =0.4$:

$\Rightarrow 0.4=1-\frac{T_c}{T_h}\Rightarrow \frac{T_c}{T}=0.6$

For $\eta =0.5$:

$\Rightarrow 0.5=1-\frac{T_c}{T_h}$

$\Rightarrow T_h=2T_c=2\left(0.6T\right)=\frac{6}{5}T$

Hence, option D is correct.