What does the surface integral of dA in Gauss' law represent?

Answer 1

You know :

Gauss law : integrate(E.dA)

dA = represents the diferential of area

is a very little part of the area of a surface, like for example a sphere.

You know that in electrostatics :

integration(E.dA) = q / Eo

where : q is the charge

E = electric field

dA = diferential of area

in the case of the sphere, dA = 4*pi*r^2*dr

pi = 3.1416