$90 \ J$ of work is done to move an electric charge of magnitude $3 \ C$ from a place $A$,where potential is $-10 \ V$,to another place $B$,where potential is $V_1 \ V$. The value of $V_1$ is: (in $V$)

$A$ regular hexagon of side $9 \ cm$ has a charge $5 \mu C$ at each of its vertices. The electric potential at its centre is $..........V$. $(k = 9 \times 10^9 \ Nm^2 C^{-2})$

Can the potential function have a maximum or minimum in free space? Explain.

Electric charges having the same magnitude $q$ are placed at $x = 1 \, m, 2 \, m, 4 \, m, 8 \, m, \dots$ and so on. If any two consecutive charges have opposite signs but the first charge is necessarily positive,what will be the potential at $x = 0$?

$A$ and $C$ are concentric conducting spherical shells of radius $a$ and $c$ respectively. $A$ is surrounded by a concentric dielectric of inner radius $a$,outer radius $b$ and dielectric constant $k$. If sphere $A$ is given a charge $Q$,the potential at the outer surface of the dielectric (at radius $b$) is:

The electric potential at a distance $r$ outside a uniformly charged sphere (where $a$ is the radius of the sphere) is proportional to: