Question:
For an ideal heat engine, the temperature of the source is $127^{\circ} \mathrm{C}$. In order to have $60 \%$ efficiency the temperature of the sink should be___________ ${ }^{\circ} \mathrm{C}$. (Round off to the Nearest Integer)
Solution:
Ans. (-113)
$\mathrm{n}=0.60=1=\frac{\mathrm{T}_{\mathrm{L}}}{\mathrm{T}_{\mathrm{H}}}$
$\frac{\mathrm{T}_{\mathrm{L}}}{\mathrm{T}_{\mathrm{H}}}=0.4 \Rightarrow \mathrm{T}_{\mathrm{L}}=0.4 \times 400$
$=160 \mathrm{~K}$
$=-113^{\circ} \mathrm{C}$