Figure shows a solid hemisphere with a charge of $5\ nC$ distributed uniformly through its volume. The hemisphere lies on a plane and point $P$ is located on this plane, along a radial line from the centre of curvature at distance $15\ cm$. The electric potential at point $P$ due to the hemisphere, is .....$V$

Two charges of magnitude $+ q$ and $-\,3q$ are placed $100\,cm$ apart. The distance from $+ q$ between the charges where the electrostatic potential is zero is.......$cm$

In the following figure two parallel metallic plates are maintained at different potential. If an electron is released midway between the plates, it will move

$A$ 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.

A table tennis ball which has been covered with conducting paint is suspended by a silk thread so that it hang between two plates, out of which one is earthed and other is connected to a high voltage generator. This ball

Write the relation between the electric field of an electric charge and electrostatic potential at any point.