$A$ radius of a spherical charged shell is $10 \ cm$ and the electric potential on its surface is $100 \ V$. Then,the potential at $2 \ cm$ from the centre of the shell will be $.......$ (in $V$)

Three charges $q, \sqrt{2}q$,and $2q$ are placed at the corners $A, B$,and $C$ respectively of a square $ABCD$ of side length $a$. Find the electric potential at point $D$.

$A$ conductor with a positive charge:

$729$ small identical spheres each charged to an electric potential $3 \ V$ combine to form a bigger sphere. The electric potential of the bigger sphere is (in $V$)

Three point charges $+Q$,$+2Q$,and $q$ are placed at the vertices of an equilateral triangle. The value of charge $q$ in terms of $Q$,so that the electrical potential energy of the system is zero,is given by:

$A$ charge of total amount $Q$ is distributed over two concentric hollow spheres of radii $r$ and $R$ $(R > r)$ such that the surface charge densities on the two spheres are equal. The electric potential at the common centre is