A Carnot's engine has an efficiency of 50% at sink temperature 50⁰C. Calculate the temperature of source. 

Efficiency of Carnot's engine,  $\eta =1-\frac{T_2}{T_1}$   …(i)

where, T₂ is temperature of sink and T₁ is the temperature of the source.

Here,   $\eta =50\mathrm{\%},T_2={50}^{\circ }\mathrm{C}=50+273=323\mathrm{K}$

Putting these values in Eq. (i), we get 

$\frac{50}{100}=1-\frac{323}{T_1}$

$\Rightarrow T=646\mathrm{K}={373}^{\circ }\mathrm{C}$