Draw a graph of $V \to r$ for spherical shell.

$N$ identical spherical drops charged to the same potential $V$ are combined to form a big drop. The potential of the new drop will be

Two point charges $4\,\mu C$ and $ - 1\,\mu C$ are kept at a distance of $3\ m$ from each other. What is the electric potential at the point where the electric field is zero?......$V$

Three concentric spherical metallic shells $X , Y$ and $Z$ of radius $a , b$ and c respectively $[ a < b < c ]$ have surface charge densities $\sigma,-\sigma$ and $\sigma$, respectively. The shells $X$ and $Z$ are at same potential. If the radii of $X$ and $Y$ are $2\,cm$ and $3\,cm$, respectively.The radius of shell $Z$ is $......cm$.

A hollow metallic sphere of radius $R$ is given a charge $Q$. Then the potential at the centre is

A hollow metallic sphere of radius $10 \;cm$ is charged such that potential of its surface is $80\; V$. The potential at the centre of the sphere would be