Question

A thermodynamic cycle in the pressure $(P)$-volume $(V)$ plane is given below:

$AB$ and $CD$ are isothermal processes while $BC$ and $DA$ are adiabatic processes. The same cycle in the temperature $(T)$ - entropy $(S)$ plane is :

• A.
• B.
• C.
• D.

Answer 1

Answer: (A)

$AB$ is isothermal reversible expansion process i.e. $\Delta T=0$ and $S$ increases as there is increase in volume.
$BC$ is adiabatic reversible expansion process $\left(q_{rev}=0\right)$ i.e. temperature decreases and $\Delta S=0$
$CD$ is isothermal reversible compression process i.e. $\Delta T=0$ and $S$ decreases as there is decrease in volume.
$DA$ is adiabatic reversible compression process $\left(q_{rev}=0\right)$ i.e. temperature decreases and $\Delta S=0$