Write an equation for potential at a point in a uniformly charged spherical shell.

$STATEMENT-1$ For practical purposes, the earth is used as a reference at zero potential in electrical circuits.and

$STATEMENT-2$ The electrical potential of a sphere of radius $R$ with charge $\mathrm{Q}$ uniformly distributed on the surface is given by $\frac{\mathrm{Q}}{4 \pi \varepsilon_0 R}$.

Twenty seven drops of same size are charged at $220\, \mathrm{~V}$ each. They combine to form a bigger drop. Calculate the potential of the bigger drop. (In $\mathrm{~V}$)

Four charges of $1\  \mu C, 2\  \mu C, 3\  \mu C,$ and $- 6\ \mu C$ are placed one at each corner of the square of side $1\,m$. The square lies in the $x-y$ plane with its centre at the origin.

In a regular polygon of $n$ sides, each corner is at a distance $r$ from the centre. Identical charges are placed at $(n - 1)$ corners. At the centre, the intensity is $E$ and the potential is $V$. The ratio $V/E$ has magnitude.

Find the equation of the equipotential for an infinite cylinder of radius ${{r_0}}$, carrying charge of linear density $\lambda $.