Note 1 to entry: Maxwell’s equations expressed in differential form are:

${\displaystyle \mathrm{rot}E=-\frac{\partial B}{\partial t}}$

$\text{div}D=\rho$

${\displaystyle \mathrm{rot}H=J+\frac{\partial D}{\partial t}}$

$\text{div}B=0$

where rot and div denote the rotation and the divergence respectively, E, D, H and B are the four vector quantities determining the electromagnetic field, J is the electric current density, ρ is the volumic electric charge and t is the time.

Note 2 to entry: Maxwell’s equations completely define the electromagnetic field in a given medium only together with the relations characterizing the medium, often called constitutive relations; in the case of a linear medium, these relations are expressed in terms of the absolute permittivity, the absolute permeability, and the conductivity of the medium.