# Isochoric Process

### 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 = mCV (T₂ – T₁)

U₂ – U₁ = mCV (T₂ – T₁)

Heat supplied or Heat Transfer:

Q₁₋₂ = dU + W₁₋₂

Q₁₋₂ = U₂ – U₁ = mCp (T₂ – T₁)

Change in Enthalpy:

H = mCp (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. W₁₋₂ is -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).