Electron volt is a unit of

Two point charges $-q$ and $+q$ are located at points $(0,0,-a)$ and $(0,0, a)$ respectively. The electric potential at a point $(0,0, z)$,where $z>a$ is

Three concentric metallic shells $A, B$ and $C$ of radii $a, b$ and $c$ $(a < b < c)$ have surface charge densities $\sigma, -\sigma$ and $\sigma$ respectively. Find the potentials ${V_A}$ and ${V_B}$.

The potential at point $A$ is $3 \ V$ and at point $B$ is $7 \ V$. An electron is moving towards $A$ from $B$. Which of the following statements is correct?

Prove that electrostatic forces are conservative in nature and define electrostatic potential energy.

There are three concentric conducting spherical shells $A$,$B$,and $C$ of radii $a$,$b$,and $c$ respectively. The potentials of the spheres $A$,$B$,and $C$ respectively are: