Adiabatic Relation

Thermodynamics · 1823

Equation: p V^γ = constant
Field: Thermodynamics
Named After: Siméon Denis Poisson
Symbols: p pressure · V volume · γ = c_p/c_v ratio of specific heats, 1.4 for diatomic gases
Year: 1823

Significance

How a gas behaves when compressed or expanded too fast to exchange heat — the compression and power strokes of every piston engine, and the compressor and turbine of every jet. It is the curve the cycle diagrams on this site are drawn with, and the reason a bicycle pump gets hot.

Machines

Otto Four-Stroke Engine Stirling Engine Wankel Rotary Engine Diesel Engine Gas Turbine (Jet Engine)

Requires

First Law of Thermodynamics Ideal Gas Law

Required By

Otto Cycle Efficiency Diesel Cycle Efficiency Brayton Cycle Efficiency Newton–Laplace Speed of Sound

Referenced by

equation

Brayton Cycle Efficiency Diesel Cycle Efficiency First Law of Thermodynamics Ideal Gas Law Newton–Laplace Speed of Sound Otto Cycle Efficiency

machine

Diesel Engine Gas Turbine (Jet Engine)Otto Four-Stroke Engine Stirling Engine Wankel Rotary Engine

Open on the Equations shelf — the interactive card, the filters, and everything alongside it.

From the Equations database in Notion, last edited 2026-08-18. This page is the row, rendered by the build; nothing on it is written by hand.