The minimum work needed to be done to bring a charge $q=6 \mu C$ from $\infty$ to a point $0.75 \ m$ from a charge $Q=30 \mu C$ is (in $J$)

The electric potential at a point at a distance $x$ from the center inside a conducting sphere of radius $R$ charged with charge $Q$ is:

Three charges $q, \sqrt{2}q$,and $2q$ are placed at the corners $A, B$,and $C$ respectively of a square $ABCD$ of side length $a$. Find the electric potential at point $D$.

Statement-$1$: For a charged particle moving from point $P$ to point $Q$,the net work done by the electrostatic force is independent of the path connecting point $P$ to point $Q$.
Statement-$2$: The net work done by a conservative force on an object in a closed loop is zero.

The work done to assemble the three charges in a configuration as shown in the figure is

$A$ 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 $K = \frac{1}{4\pi\varepsilon_0}$):