We know from Gauss Law that the closed surface integral of electric flux density () is equal to the charge enclosed () by that closed surface. This is mathematically given by
The electric flux is given by
Let us consider a point charge +q with electric field lines going away from it. We will consider following two scenarios
Scenario 1: Gaussian surface S is chosen around +q charge as shown below
From the Gauss’s law, the expression (2) will be
Also, we can see that the flux lines are going outward from the surface.
Scenario 2: Gaussian surface S is chosen as shown in the figure below
We can see that there is no charge inside the chosen surface S and all the charge is outside of this surface. Also, same number of electric flux lines entering this surface emerges out from this surface. Therefore, by Gauss’s law, the expression (2) will be
However, is not zero.
Therefore, option C and D are correct.
Rate this question :