Three concentric spherical metallic shells $A$,$B$,and $C$ of radii $a=7 \ cm$,$b=17 \ cm$,and $c$ $(a < b < c)$ have surface charge densities $\sigma, -\sigma$,and $\sigma$ respectively. If $A$ and $C$ are at the same potential,then the value of $c$ is: (in $cm$)

The charge given to a hollow sphere of radius $10\, cm$ is $3.2 \times 10^{-19}\, C$. At a distance of $4\, cm$ from its centre,the electric potential will be

$A$ charge $Q$ is distributed over three concentric spherical shells of radii $a, b, c$ $(a < b < c)$ such that their surface charge densities are equal to one another. The total potential at a point at distance $r$ from their common centre,where $r < a$,would be

The electric potential on the surface of a charged spherical conductor of radius $5 \,cm$ is $200 \,V$. The work done in moving a charge of $+5 \,C$ from a point $A$ to another point $B$ situated at distances of $15 \,cm$ and $10 \,cm$ respectively from the centre of the sphere is (in $\,J$)

Two identical thin rings each of radius $R \text{ m}$ are kept on the same axis at a distance of $R \text{ m}$ apart. If the charges on them are $10 \text{ C}$ and $5 \text{ C}$ respectively,calculate the work done in moving a charge '$q$' coulomb from the centre of one ring to that of another.

An electric charge $10^{-3} \, \mu C$ is placed at the origin $(0, 0)$ of an $X-Y$ coordinate system. Two points $A$ and $B$ are situated at $(\sqrt{2}, \sqrt{2})$ and $(2, 0)$ respectively. The potential difference between the points $A$ and $B$ will be $V$.