Gauss's Law

A fundamental electromagnetic law stating that the net electric flux through any closed surface equals the total electric charge enclosed by that surface divided by the permittivity of free space (ε0).

In classical electromagnetism, the net electric flux of the electric field E through any closed surface S equals the total electric charge Q_enclosed within S divided by the permittivity of free space ε0: ∮_S E·dA = Q_enclosed/ε0. Equivalently, in differential form, ∇·E = ρ/ε0, relating the local divergence of E to charge density ρ.