Two points $P$ and $Q$ are maintained at the potentials of $10\, V$ and $-4\, V$,respectively. The work done in moving $100$ electrons from $P$ to $Q$ is:

Six charges $+q, -q, +q, -q, +q$ and $-q$ are fixed at the corners of a hexagon of side $d$ as shown in the figure. The work done in bringing a charge $q_0$ to the centre of the hexagon from infinity is: ($\varepsilon_0$ = permittivity of free space)

There are two thin wire rings,each of radius $R$,whose axes coincide. The charges of the rings are $q$ and $-q$. The magnitude of potential difference between the centres of the rings separated by a distance $\sqrt{3} R$ is

Identical charges $(-q)$ are placed at each corner of a cube of side $b$. The electrostatic potential energy of a charge $(+q)$ placed at the center of the cube is:

$A$ charge $(-q)$ and another charge $(+Q)$ are kept at two points $A$ and $B$ respectively. Keeping the charge $(+Q)$ fixed at $B$,the charge $(-q)$ at $A$ is moved to another point $C$ such that $ABC$ forms an equilateral triangle of side $l$. The net work done in moving the charge $(-q)$ is

Three identical charges of $10 \ \mu C$ are placed at the vertices of an equilateral triangle of side $10 \ cm$. The electrostatic potential energy of the system is ....... $J$.