The maximum possible efficiency of a heat engine is ...........

Explain why the efficiency of a Carnot engine cannot be $100\%$?

$A$ Carnot heat engine has an efficiency of $20 \%$. The energy is supplied to the engine at the rate of $2 \text{ kW}$. The output power of the engine is (in $\text{ W}$)

$A$ diatomic ideal gas is used as the working substance in a Carnot engine. During the adiabatic expansion process,if the volume of the gas increases from $V$ to $32V$,what is the efficiency of the engine?

If a Carnot engine works between $127^{\circ} C$ and $527^{\circ} C$,then its efficiency is ...... $\%$

$A$ heat engine operates with the cold reservoir at a temperature of $324 \; K$. If the heat engine takes $300 \; J$ of heat from the hot reservoir and delivers $180 \; J$ of heat to the cold reservoir per cycle,what is the minimum temperature of the hot reservoir in $K$?