For a closed Gaussian surface , electric flux is given by : where E is the electric field , S is any closed surface , Q is the total electric charge inside the surface S , ε0 is the electric constant ( a universal constant , also called the `` permittivity of free space '' ) ( ε0 ≈ 8.854 187 817 ... x 10 − 12 farads per meter ( F · m − 1 ) ) .
For a closed Gaussian surface , electric flux is given by : where QS is the net charge enclosed by the surface ( including both free and bound charge ) , and ε0 is the electric constant .