State which of the following is correct.

$A$ particle has a mass $400$ times that of an electron and a charge double that of an electron. It is accelerated by a potential difference of $5 \ V$. If the particle was initially at rest,what will be its final kinetic energy in $eV$?

$A$ long,hollow conducting cylinder is kept coaxially inside another long,hollow conducting cylinder of larger radius. Both the cylinders are initially electrically neutral.

The value of the electric potential at a point due to a point charge is:

An electric point charge $10^{-3} \mu C$ is placed at the origin $(0, 0)$ of an $X-Y$ coordinate system. Two points $A$ and $B$ are situated at $(\sqrt{2}, \sqrt{2})$ and $(2, 0)$ respectively. The potential difference between the points $A$ and $B$ will be.....$volt$.

$A$ total charge $Q$ is distributed between two concentric spherical shells of radii $r$ and $R$ $(R > r)$ such that their surface charge densities are equal. What is the electric potential at their common center?