If the thermodynamic system is perfectly conducting to the surrounding, and undergoes a physical process in such a way that its tempreture remains constant throughout,the process is said to be isothermal process.
It may be defined as
“ A change in pressure & volume of gas without any change in its tempreture is called an isothermal process or isothermal operation”.
For such process, tempreture of the system remains constant,
i.e. T = constant
& △T = 0
Essential Conditions for Perfect Isothermal Process :-
1. The wall of container must be perfectly conducting.
2.The process of compression or expansion should be so slow so as to provide time for exchange of heat.
Equation of an Isothermal Change :-
Using equation of Vanderwall’s gas
PV = nRT
If n = 1mol, R = constant, T= constant
PV = K(constant)
This is equation of Isothermal Change.
Specific Heat Capacity of Isothermal Change :-
In an Isothermal change, T = constant
then △T = 0
As, specific heat of gas is given by
C = △Q/m△T
∵ △T =0
∴ C = ∞
Therefore, in an Isothermal change apecific heat of gas is infinite.