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 metal spheres of radii ${R_1}$ and ${R_2}$ are charged to the same potential. The ratio of charges on the spheres is

Charges of $ + \frac{{10}}{3} \times {10^{ - 9}}C$ are placed at each of the four corners of a square of side $8\,cm$. The potential at the intersection of the diagonals is

Two unlike charges of magnitude $q$ are separated by a distance $2d$. The potential at a point midway between them is

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

A charge $+q$ is distributed over a thin ring of radius $r$ with line charge density $\lambda=q \sin ^{2} \theta /(\pi r)$. Note that the ring is in the $X Y$ - plane and $\theta$ is the angle made by $r$ with the $X$-axis. The work done by the electric force in displacing a point charge $+ Q$ from the centre of the ring to infinity is