Equilibrium

A systems have reached equilibrium when there is no change in the macroscopic state of the system.

Equilibrium of some common systems are described below. Note that the properties describing the state of a system depends on the boundary of the system.

Mechanical Equilibrium

• Mechanical systems have reached equilibrium when there is no movement between the systems

Thermal Equilibrium

• Thermodynamic systems have reached equilibrium when there is no heat transfer between the systems

This state of equilibrium requires the systems to have the same temperature.

Electrostatic Equilibrium

• Electrostatic systems have reached equilibrium when there is no net charge flow between the systems

Phase Equilibrium

• Material substance systems have reached equilibrium when there is no net phase transformation, like melting, between the systems.

Chemical Equilibrium

• Chemical systems have reached equilibrium when there is no net chemical reaction between the system