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

$A$ spherical shell with an inner radius $a$ and an outer radius $b$ is made of conducting material. $A$ point charge $+Q$ is placed at the centre of the spherical shell and a total charge $-q$ is placed on the shell. Assume that the electrostatic potential is zero at an infinite distance from the spherical shell. The electrostatic potential at a distance $R$ $(a < R < b)$ from the centre of the shell is (where $K = \frac{1}{4\pi\varepsilon_0}$):

Draw a graph showing the variation of electric potential $V$ with distance $r$ from the center for a uniformly charged spherical shell of radius $R$.

$A$ metal sphere of radius $r$ carrying charge $q$ is placed at the center of a metallic shell of radius $R$ carrying charge $Q$. Find the expression for the potential difference between the sphere and the shell.

Electric charges $+q$ and $-q$ are placed at points $A$ and $B$ respectively,which are at a distance of $2L$ apart. If $C$ is the midpoint between $A$ and $B$,then the work done in moving a charge $+Q$ along the semi-circle $CRD$ is

Charges $Q$ are placed at each corner of a square of side $a$. How much work is required to remove a charge $-Q$ from the center of the square and move it to infinity?