$A$ 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 is.

Two large vertical and parallel metal plates having a separation of $1 \ cm$ are connected to a $DC$ voltage source of potential difference $X$. A proton is released at rest midway between the two plates. It is found to move at $45^{\circ}$ to the vertical $JUST$ after release. Then $X$ is nearly

A charge of ${10^{ – 9}}\,C$ is placed on each of the $64$ identical drops of radius $2\,cm$. They are then combined to form a bigger drop. Find its potential

Variation in electric potential is maximum if one goes

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