Gauss flux theorem The surface integral of the normal component of the electric field over a closed surface equals the total charge inside the enclosed volume divided by permittivity of free space (e ₀ ). Mathematically,

ò E.ds =q/e ₀

In the differential form it can be written as,

div E = r / e ₀

where r is the charge density at a point in space where the electric field is E. See also Maxwell’s equations.