$A$ charge $q$ is placed at the center of a cubical box of side $a$ with the top open. The flux of the electric field through one of the five closed surfaces of the cubical box is:

$A$ charge '$Q$ $\mu C$' is placed at the centre of a cube. The flux through one face and two opposite faces of the cube is respectively:

$A$ 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 $20 \ cm$?

$A$ point charge $+q$ is placed at the centre of a cube of side $L$. The electric flux emerging from the cube is

The figure shows the electric lines of force emerging from a charged body. If the electric field at $A$ and $B$ are $E_A$ and $E_B$ respectively,and if the distance between $A$ and $B$ is $r$,then:

$A$ thin spherical shell encloses a concentric solid sphere. The radius of the shell is $(0.060)^{1/2} \ m$ and its surface charge density is $-10^{-5} \ C/m^2$. The radius of the solid sphere is $(0.01)^{1/3} \ m$ and its volumetric charge density is $3 \times 10^{-5} \ C/m^3$. $\varepsilon_0$ is the permittivity of free space in $C^2/Nm^2$. The electric flux through a spherical surface concentric with the spherical shell and of radius greater than that of the shell in $V-m$ is: