Question

In thermodynamic processes which of the following statements is not true?
A. In an adiabatic process $P{V^r}$= constant
B. In an adiabatic process the system is insulated from the surroundings
C. In an isochoric process pressure remains constant
D. In an isothermal process the temperature remains constant

Answer 1

To solve this question, let’s first understand some concepts of thermodynamic processes. From the ideal gas law, we know that $P{V^r}$ = constant. So, PV = nRT = constant. This means that the product of the pressure of a gas times the volume of a gas is a constant for a given sample of gas.

Complete step by step answer:
First, let’s note the meaning of adiabatic, isochoric and isothermal processes. We know that when a process is carried out such that no heat flows from the system to the surroundings or vice versa then the process is called an adiabatic process. Whereas an isochoric process is a thermodynamic process in which the volume of the closed system undergoing will remain constant. And when a process is carried out in such a way that the temperature remains constant throughout the process then it is called an isothermal process.
So, from referring to these concepts we will solve the above question.
The first statement that an adiabatic process $P{V^r}$ = constant is true.
In an adiabatic process, the system gets insulated from the surroundings. An adiabatic process is one that occurs without the transfer of heat or mass of substances between a thermodynamic system and its surroundings. So, in the adiabatic process insulation from surroundings is required which is true.
In an isochoric process, volume remains constant. Therefore, the option C is incorrect.
In an isothermal process, the temperature remains constant which is true.

So, the correct answer is Option C.

Note:
As we know, in an isobaric process is a process during which the pressure of the system remains constant. And a system is known to be in thermodynamic equilibrium when its macroscopic properties like temperature, pressure do not change with time.