No current flows between two charged bodies connected together when they have the same

$A, B$ and $C$ are three points in a uniform electric field as shown in the figure. The electric potential is

Define electrostatic potential energy.

$A$ point charge $q$ of mass $m$ is placed at the center of a ring of radius $R$ carrying a charge $Q$. When it is slightly displaced,the point charge accelerates to infinity along the $x$-axis. The ultimate speed of the point charge is .......

$A$ small conducting sphere of radius $r$ is lying concentrically inside a bigger hollow conducting sphere of radius $R$. The bigger and smaller spheres are charged with $Q$ and $q$ respectively $(Q > q)$ and are insulated from each other. The potential difference between the spheres will be

Particle $A$ has a charge of $+q$ and particle $B$ has a charge of $+4q$. Both particles have the same mass. If they are released from rest under the same electric potential difference,what is the ratio of their speeds $V_A / V_B$?