Classical thermodynamics, heat transfer Definition

Quasistatic process

Builds on Thermodynamic state Thermodynamic equilibrium

Definition

Let $\mathcal{S}$ be the set of equilibrium states of a thermodynamic system $\Sigma$ . A process of $\Sigma$ is quasistatic if $\Sigma$ is in an equilibrium state at every time of the process. Such a process is described by a continuous curve $\gamma \colon [0, 1] \to \mathcal{S}$ .

Remarks

Expanding a gas in a cylinder very slowly against a piston, at each moment balancing the gas pressure, is quasistatic. The free expansion of a gas into a vacuum, after a wall is removed, is not quasistatic. During it, the gas is not in an equilibrium state, so it has no well-defined pressure. A quasistatic process need not be reversible: slow expansion against a piston with friction is quasistatic but dissipates energy.

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Tag	`XY4P76C13P`
URI	`m2://XY4P76C13P`
Kind	definition
Writing	W0 stub
MSC	80A05, 80A10
Defines	Quasistatic process
Uses	Thermodynamic state, Thermodynamic equilibrium
Changed	3 November 2026

Quasistatic process

Definition

Remarks

Reading path

Further reading

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