$A$ heat engine receives $200 \, cal$ of heat and rejects $150 \, cal$ of heat. If the temperature of the source is $400 \, K$,what is the temperature of the sink in $K$ (in $, K$)?

$A$ Carnot engine takes $3 \times 10^6$ calories of heat from a reservoir at $627^{\circ} C$ and gives it to a sink at $27^{\circ} C$. The work done by the engine is

$A$ Carnot engine uses an ideal monoatomic gas first and then an ideal diatomic gas. If the source and sink temperatures are $411^{\circ}C$ and $69^{\circ}C$ respectively,and the engine extracts $1000 \, J$ of heat in each cycle,then the area enclosed by the $PV$ diagram is ........ $J$.

What is the efficiency of a heat engine? Write its formula.

Three Carnot engines operate in series between a heat source at a temperature $T_1$ and a heat sink at temperature $T_4$ (see figure). There are two other reservoirs at temperatures $T_2$ and $T_3$,as shown,with $T_1 > T_2 > T_3 > T_4$. The three engines are equally efficient if

Consider a reversible engine of efficiency $\frac{1}{6}$. When the temperature of the sink is reduced by $62^{\circ} C$, its efficiency gets doubled. The temperature of the source and sink respectively are