An adiabatic process is one in which the system undergoes no heat transfer with the surroundings, but the boundary of the system moves giving displacement work. The arrangement for the adiabatic process is shown in the figure below. It consists of a piston-cylinder arrangement where the cylinder is insulated from all sides to prevent heat transfer.
Since (△Q = 0), therefore (△W) is only due to (△U). The (P-V) diagram for an adiabatic process is shown in the figure below.
Applying the first law of thermodynamics:
