Written by the Fiveable Content Team • Last updated August 2025
Written by the Fiveable Content Team • Last updated August 2025
Definition
An adiabatic process is a thermodynamic process in which no heat is exchanged with the surroundings. The system's temperature can change, but all energy transfer occurs as work.
In an adiabatic process, $Q = 0$, where $Q$ represents heat transfer.
Adiabatic processes are often idealized and occur very rapidly or within perfectly insulated systems.
For an adiabatic compression or expansion of an ideal gas, the relationship between pressure and volume follows $PV^\gamma = \text{constant}$, where $\gamma$ is the heat capacity ratio ($C_p/C_v$).
The first law of thermodynamics for an adiabatic process simplifies to $\Delta U = W$, where $\Delta U$ is the change in internal energy and $W$ is work done by or on the system.
Real-life examples of nearly adiabatic processes include atmospheric phenomena like the rapid ascent or descent of air parcels.
A thermodynamic process in which the temperature remains constant, meaning any heat added to the system does work or vice versa.
Heat Capacity Ratio: $\gamma$ (gamma), also known as the adiabatic index, is the ratio of specific heat at constant pressure ($C_p$) to specific heat at constant volume ($C_v$).