In physics, a conservation law states that a particular measurable property of an isolated physical system does not change as the system evolves. The following is a partial listing of conservation laws that have never been shown to be inexact.

• conservation of energy
• conservation of momentum
• conservation of angular momentum
• conservation of electric charge
• conservation of color charge
• CPT symmetry

The fundamental idea of charge conservation is contained in Maxwell's Equations. If we take the divergence of the differential form of Ampere's law:

The first term above is zero by identity, and using Gauss's law:

the result is:

The implication here is that the current through any enclosed surface is equal to the time rate of charge within the surface. This is an important test of Maxwell's equations since all experimental evidence points to charge conservation.