$A$ 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 $^oC$?

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

Two ideal Carnot engines operate in cascade (all heat given up by one engine is used by the other engine to produce work) between temperatures $T_{1}$ and $T_{2}$. The temperature of the hot reservoir of the first engine is $T_{1}$ and the temperature of the cold reservoir of the second engine is $T_{2}$. $T$ is the temperature of the sink of the first engine,which is also the source for the second engine. How is $T$ related to $T_{1}$ and $T_{2}$,if both engines perform equal amounts of work?

$A$ 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 $, K$)?

$A$ frictionless heat engine can be $100 \%$ efficient only if its exhaust temperature is ............

$A$ scientist claims that their heat engine has an efficiency of $26\%$ when operating between a source temperature of $127^{\circ}C$ and a sink temperature of $27^{\circ}C$. This implies that: