Question

Which of the following is isentropic process
A. Isothermal
B. Adiabatic
C. Isochoric
D. Isobaric

Answer 1

Hint: Isentropic process is a process in which the entropy remains unchanged or the change in entropy is zero. Entropy represents the disorder in a system. Entropy of a system depends upon the temperature of a system.

Formula used:
Equation of state having temperature T, Volume V, Pressure P, and no of moles of substance n, is
$PV=nRT$
R= Universal gas constant the value of R is
$R=8.3145J.mo{{l}^{-1}}.{{K}^{-1}}$

Complete step by step answer:
There are four fundamental thermodynamic variables temperature \[\left( T \right)\], volume $\left( V \right)$, pressure $\left( P \right)$ and amount of substance $\left( n \right)$ present in the system. By keeping one of these variables constant and changing others we will get a different thermodynamic process.
Isothermal Process: The process in which temperature of a system remains constant but pressure and volume changes.
The equation of state for isothermal process is given by
$PV=\text{ constant}$
Adiabatic process: In adiabatic process there is no heat exchange between the system and surroundings. But the pressure, volume and temperature changes.
The equation of adiabatic state is $P{{V}^{\gamma }}=\text{constant}$
Where $\gamma $ is the ratio of molar specific heat at constant pressure to the molar specific heat at constant volume.
Isochoric process: It is also called a constant volume process. In this process pressure and temperature changes but volume remains unchanged.
Equation of the state is $\dfrac{P}{T}=\text{ constant}$
Isobaric process: Also known as constant pressure process. This process is obtained by allowing the volume to expand or contract in such a way that any change in volume will be transferred to heat.
Equation of state is $\dfrac{V}{T}=\text{ constant}$
 In the processes adiabatic, isobaric and isochoric the temperature of the system changes which will lead to change in disorderness of the system that means in these processes the entropy will change.
But in the isothermal process the temperature remains constant so there will be no entropy change.
So the isentropic process is an isothermal process.
So the correct option is A.

Note:
The isothermal process is attained when there is a conducting partition between the system and surrounding. Because any change in volume or pressure will change the temperature of the system, if there is a conducting wall between the system and surrounding any temperature change will be transferred to the surrounding and the temperature of the system remains constant.