Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
An isochoric process is a thermodynamic process in which the volume remains constant. Since the volume does not change, no work is done by the system during this process.
In an isochoric process, the work done by the system is zero because $\Delta V = 0$.
The first law of thermodynamics simplifies to $\Delta U = Q$ for an isochoric process, indicating that all heat added to the system changes its internal energy.
Isochoric processes are often represented on a PV diagram as vertical lines.
Examples of isochoric processes include heating or cooling in a rigid container where volume cannot change.
Specific heat at constant volume ($C_V$) can be used to calculate changes in internal energy for ideal gases undergoing an isochoric process.
Related terms
Isobaric: A thermodynamic process in which pressure remains constant.
Adiabatic: A thermodynamic process where no heat exchange occurs with the surroundings.
Isothermal: A thermodynamic process that occurs at a constant temperature.