On rotating a point charge having a charge $q$ around a charge $Q$ in a circle of radius $r$,the work done will be:

$A$ hollow conducting sphere is placed in an electric field produced by a point charge at point $P$. If the electric potentials at points $A$,$B$,and $C$ are $V_A$,$V_B$,and $V_C$ respectively,as shown in the figure,then:

In moving from $A$ to $B$ along an electric field line,the electric field does $6.4 \times 10^{-19} \, J$ of work on an electron. If $\phi_1$ and $\phi_2$ are equipotential surfaces,then the potential difference $(V_C - V_A)$ is.....$V$.

If charge $+q$ is taken from one point to another over an equipotential surface, then

$A$ square of side $a$ has a charge $Q$ at its centre. $A$ charge $q$ is placed at one of the corners. The work required to be done in moving the charge $q$ from this corner to the diagonally opposite corner is

Equipotential surfaces associated with an electric field which is increasing in magnitude along the $x$-direction are