The quantity of electricity displaced across a given area in a dielectric. It is given by the scalar product D.dS of the electric displacement, D, and an element dS of area. Gauss’s theorem states that

where ρ_e is the volume electric charge density in a small volume element dτ. The total flux through an area surrounding a charge q is thus equal to q. This flux is unaltered by the presence of a dielectric medium.