🛡️ Adiabatic (Q = 0) — the adiabat falls faster than the isotherm

Insulate the gas so Q = 0. Now any work done on it goes straight into internal energy, so compressing it heats it up. On a P–V diagram the adiabat P·Vγ = const is steeper than the isotherm P·V = const through the same point.

Walkthrough 1 / 3

Start from one state; the shallow purple curve is the isotherm P·V = const through it.

Volume V 22 L

Adiabatic index γ 1.40

adiabat: P·Vγ = const, T·V^γ−1 = const, Q = 0 · P = — kPa · T = — K
the steep red curve is the adiabat; the shallow purple curve is the isotherm through the start

Animation speed 1.0×