Isochoric Process

An Isochoric process is a thermodynamic process in which the volume remains constant. Since the volume is constant, the system does no work (W = 0). It is also called as constant volume process, and Iso – Volumetric process or an isometric process is a thermodynamic process during which the volume of the closed system undergoing such a process remains constant. The Isochoric process here should be a Quasi – Static Process.

Relation between P, V and T:

P/T = Constant

Work done by the gas:

W₁₋₂ = P (V₂ – V₁) = 0

Change in Internal Energy:

dU = mC_V (T₂ – T₁)

U₂ – U₁ = mC_V (T₂ – T₁)

Heat supplied or Heat Transfer:

Q₁₋₂ = dU + W₁₋₂

Q₁₋₂ = U₂ – U₁ = mC_p (T₂ – T₁)

Change in Enthalpy:

H = mC_p (T₂ – T₁)

Important points:

The change in internal energy (dU) and the change in enthalpy (dH) have the same expression for each process.
During expansion or heating process, work is done by the gas (i.e. W₁₋₂ is +ve); internal energy of the gas decreases (i.e. dU is -ve) and the heat supplied to the gas (i.e. Q₁₋₂ is +ve).
During compression or cooling process, work is done on the gas (i.e. W₁₋₂is -ve); internal energy of the gas increases (i.e. dU is +ve) and the heat supplied by the gas (i.e. Q₁₋₂ is -ve).