$A$ Carnot engine has an efficiency of $25\%$. It operates between reservoirs of constant temperature with a temperature difference of $80\,K$. What is the temperature of the low-temperature reservoir in $^oC$?

An engine has an efficiency of $1/6$. When the temperature of the sink is reduced by $62^{\circ}C$,its efficiency is doubled. The temperature of the source is ....... $^{\circ}C$.

Suppose that two heat engines are connected in series,such that the heat exhaust of the first engine is used as the heat input of the second engine as shown in the figure. The efficiencies of the engines are $\eta_1$ and $\eta_2$,respectively. The net efficiency of the combination is given by

Consider a Carnot cycle operating between $T_1 = 500\,K$ and $T_2 = 300\,K$ producing $1\,kJ$ of mechanical work per cycle. Find the heat transferred to the engine by the reservoir at $T_1$ in Joules.

$A$ Carnot engine works between $27^{\circ} C$ and $127^{\circ} C$. Heat supplied by the source is $500 \ J$. The heat ejected to the sink is (in $J$):

The temperature-entropy $(T-S)$ diagram of a reversible engine cycle is given in the figure. Its efficiency is