$A$ point charge is distributed in a small volume. The electric flux through a spherical surface of radius $10 \ cm$ enclosing the charge is $20 \ Vm$. What is the electric flux through a concentric spherical surface of radius $20 \ cm$?

Two surfaces $S_1$ and $S_2$ are shown in the figure. The electric flux associated with $S_1$ is $\phi_1$ and with $S_2$ is $\phi_2$. Which of the following is correct?

Gauss's law is given by ${\epsilon _0}\oint {\vec E \cdot d\vec s} = q$. If the net charge enclosed by a Gaussian surface is zero,then .......

In a region,the electric field is given by $\overrightarrow{E}=(3 \hat{i}+5 \hat{j}+7 \hat{k}) \text{ NC}^{-1}$. The electric flux through a surface of area $3 \text{ m}^2$ in the $yz$-plane is (in $SI$ units):

The adjoining diagram shows the electric lines of force emerging from a charged body. If the electric fields at $A$ and $B$ are $E_A$ and $E_B$ respectively and the distance between them is $r$,then

$A$ disk of radius $a/4$ having a uniformly distributed charge $6 \text{ C}$ is placed in the $x-y$ plane with its centre at $(-a/2, 0, 0)$. $A$ rod of length $a$ carrying a uniformly distributed charge $8 \text{ C}$ is placed on the $x$-axis from $x = a/4$ to $x = 5a/4$. Two point charges $-7 \text{ C}$ and $3 \text{ C}$ are placed at $(a/4, -a/4, 0)$ and $(-3a/4, 3a/4, 0)$,respectively. Consider a cubical surface formed by six surfaces $x = \pm a/2, y = \pm a/2, z = \pm a/2$. The electric flux through this cubical surface is