Nine point charges are placed on a cube as shown in the figure. The charge $q$ is placed at the body centre whereas all other charges are at the vertices. The electrostatic potential energy of the system will be

A point charge $Q$ is placed in uniform electric field $\vec E = E_1 \hat i + E_2\hat j$ at position $(a, b)$. Find work done in moving it to position $(c, d)$

Three point charges $q, q$ and $-2 q$ are placed at the corners of an equilateral triangle of side '$L$'. Calculate work done by extemal force in moving all the charges far apart without acceleration

Potential atapoint $A$ is $3 $ $ volt$ and atapoint $B$ is $7$ $volt$,an electron is moving towards $A$ from $B.$

Derive the formula for the electric potential energy of system of two charges.

Charges $-q,\, q,\,q$ are placed at the vertices $A$, $B$, $C$ respectively of an equilateral triangle of side $'a'$ as shown in the figure. If charge $-q$ is released keeping remaining two charges fixed, then the kinetic energy of charge $(-q)$ at the instant when it passes through the mid point $M$ of side $BC$ is