Gauss's law is true only if the force due to a charge varies as:

Three charges $q_1 = 1\,\mu C, q_2 = 2\,\mu C$,and $q_3 = -3\,\mu C$ and four surfaces $S_1, S_2, S_3$,and $S_4$ are shown in the figure. The electric flux emerging through surface $S_2$ in $N\cdot m^2/C$ is:

$A$ point source of $3000 \ lumen$ is located at the centre of a cube of side length $2 \ m$. The flux through one side is......$lumen$.

$A$ charge is kept at the central point $P$ of a cylindrical region. The two edges subtend a half-angle $\theta$ at $P$, as shown in the figure. When $\theta=30^{\circ}$, then the electric flux through the curved surface of the cylinder is $\Phi$. If $\theta=60^{\circ}$, then the electric flux through the curved surface becomes $\Phi / \sqrt{n}$, where the value of $n$ is. . . . . . .

Two equations are given below:
$A. \oint E \cdot dA = \frac{Q}{\varepsilon_0}$
$B. \oint B \cdot dA = 0$
They are:

If the number of electric lines of force emerging out of a closed surface is $1000$,then the charge enclosed by the surface is .......... $C$.