## Quick Reference

A set of differential equations describing the space and time dependence of the electromagnetic field and forming the basis of classical electrodynamics. They were proposed in 1864 by James Clerk Maxwell. In SI units the equations are:

(1) div*D* = ρ

(2) curl*E* = −∂*B*/∂*t*

(3) div*B* = 0

(4) curl*H* = ∂*D*/∂*t* + *J*

where *D* is the electric displacement, *E* is the electric field strength, *B* is the magnetic flux density, *H* is the magnetic field strength, ρ is the volume charge density, and *J* is the electric current density. Note that in relativity and particle physics it is common to use Gaussian units or Heaviside–Lorentz units, in which case Maxwell's equations include 4π and the speed of light *c*. Maxwell's equations have the following interpretation. Equation (1) represents Coulomb's law; equation (2) represents Faraday's laws of electromagnetic induction; equation (3) represents the absence of magnetic monopoles; equation (4) represents a generalization of Ampère's law.

*Subjects:*
Physics.

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