Isochoric process: This is a thermodynamic process in which the volume of the system is kept constant.But pressure, temperature and internal energy continue to be variables.
The pressure – volume graph for an isochoric process is a vertical line parallel to pressure axis as shown in Figure.
The equation of state for an isochoric process is given by
We can infer that the pressure is directly proportional to temperature. This implies that the P-T graph for an isochoric process is a straight line passing through origin. If a gas goes from state (Pi ,Ti) to (Pf, Tf) at constant volume, then the system satisfies the following equation
For an isochoric processes, ∆V = 0 and W = 0. Then the first law becomes
∆U = Q …(3)
Implying that the heat supplied is used to increase only the internal energy. As a result the temperature increases and pressure also increases.
Suppose a system loses heat to the surroundings through conducting walls by keeping the volume constant, then its internal energy decreases. As a result the temperature decreases; the pressure also decreases.
