A spherical drop of mercury having a potential of $2.5\, V$ is obtained as a result of merging $125$ droplets. The potential of constituent droplets would be........$V$

Three charged concentric nonconducting shells are given as shown in figure. Find the potential at point $A$

The electric potential at the surface of an atomic nucleus $(z=50)$ of radius $9 \times 10^{-13} \mathrm{~cm}$ is ________$\times 10^6 \mathrm{~V}$.

Charges are placed on the vertices of a square as shown. Let $E$ be the electric field and $V$ the potential at the centre. If the charges on $A$ and $B$ are interchanged with those on $D$ and $C$ respectively, then 

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.

Electric charges of $+10\,\mu\, C, +5\,\mu\, C, -3\,\mu\, C$ and $+8\,\mu\, C$ are placed at the corners of a square of side$\sqrt 2\,m$ . The potential at the centre of the square is