GAUSS’S LAW

The total outward electric flux ψ through any closed surface is equal to the total charge enclosed by the surface.
In equation form, Gauss’s law is written as

Which is the first of the four Maxwell’s equations to be derived.
Equation (2.4) states that the volume charge density is the same as the divergence of the electric flux density.

Note:

• Equations (2.3) and (2.4) are basically stating Guass’ law in different ways; equation (2.3) is the integral form and eq (2.4) is the point form or differential form of Gauss’s law.
• For symmetrical charge distributions, Gauss’s law provides an easy means of finding D or E.