Statement of Gauss's law
Gauss's law allows one to solve some problems involving charge distributions on conductors, and to calculate the electric field of several simple charge configurations. It is a mathematically equivalent form of Coulomb's law.
Gauss's law relates the flux F of electric field that "leaves" through a closed surface, to the total charge interior to that surface. The formula is
F = (E)(A)(cos q) = 4 p k Q
where E is the electric field, A is the surface area, and Q is the charge enclosed by the surface. The angle q is the angle between E and the normal to the surface. In all of our applications of Gauss's law, the electric field will be perpendicular to the surface, so q will be equal to 0 and therefore the factor cos q will simply be equal to 1.
We have to live with a perverse tradition that the constant k is frequently written as 1/(4 p e0), where e0 = 1/(4 p k) = 8.85e-12. So Gauss's law also may be seen written in the form F = Q / e0 .