What is a Carnot cycle? Explain it by drawing a figure.

(N/A) Carnot cycle is a theoretical thermodynamic cycle proposed by Sadi Carnot. It describes the most efficient possible heat engine operating between two heat reservoirs at temperatures $T_{1}$ (source) and $T_{2}$ (sink),where $T_{1} > T_{2}$.
The cycle consists of four reversible processes:
$1$. Reversible isothermal expansion: The gas expands at a constant temperature $T_{1}$,absorbing heat $Q_{1}$ from the source.
$2$. Reversible adiabatic expansion: The gas expands further without heat exchange,and its temperature drops from $T_{1}$ to $T_{2}$.
$3$. Reversible isothermal compression: The gas is compressed at a constant temperature $T_{2}$,rejecting heat $Q_{2}$ to the sink.
$4$. Reversible adiabatic compression: The gas is compressed further without heat exchange,and its temperature rises from $T_{2}$ back to $T_{1}$.
The $P-V$ diagram for the Carnot cycle is shown in the figure.