Adiabatic process

Remarks

Then the change of internal energy equals the work done on the system: $\Delta U = W$. For a reversible adiabatic process of an ideal gas with constant heat capacities, $p V^\gamma$ is constant. Here $\gamma = C_p / C_V$ is the ratio of the heat capacities at constant pressure and constant volume. The free expansion of a gas in an insulated container is adiabatic, but it is not reversible. The isothermal expansion of an ideal gas is not adiabatic: the gas absorbs heat equal to the work it does.