Question

Why entropy is constant in a reversible adiabatic process.

Answer 1

The reason for constant entropy in a reversible adiabatic process

1. In a reversible adiabatic process, the heat exchange is zero because the system is isolated from the surrounding.

From the equation of the entropy

$S_f-S_i=\int \frac{∆Q}{T}$

Here,

$$\begin{gathered} S_f=Entropyoffinalstate \\ {S}_i=Entropyofinitialstate \\ ∆Q=Changeinheat \\ T=Tempratureinkelvin \end{gathered}$$

Now, if the process is reversible adiabatic then,

$∆Q=0$

Therefore, the change in entropy of the system is also zero i.e. entropy of the system is constant.

Hence, the entropy is constant for the reversible adiabatic process.