Question

A point charge of 2 micro Coulomb is at the centre of a cubic Gaussian surface 9 cm on edge. What is the net electric flux through the surface?

Answer 1

According to Gauss theorem,
electric flux is the ratio of charge inclosed into the Gaussian surface and permittivity of medium. e.g.,

here, q is charge inclosed into the Gaussian surface.
given, q = 2 × 10^-6 C and
=8.85 × 10^-12 C²/Nm²

now, electric flux = 2 × 10^-6/8.85 × 10^-12
= 0.23 × 10^6 Nm²/C

hence, electric flux through the surface is 2.3 × 10^5 Nm²/C