In the figure shown,the electric potential energy of the system is: ($q$ is at the centre of the conducting neutral spherical shell of inner radius $a$ and outer radius $b$)

The potential energy of a system of two equal negative point charges of $2 \mu C$ each,held $1 \ m$ apart in air,is . . . . . . . $\left( k = 9 \times 10^9 \text{ SI units} \right)$

The work required to be done to assemble four particles,each having a charge $+q$,at the four corners of a square of side $a$ is .......

Two negative charges,each of magnitude $q$,are separated by a distance of $2r$. $A$ positive charge $q$ is placed at their center. The potential energy of the system is $U_1$. If the two negative charges are interchanged with the positive charge such that the new potential energy is $U_2$,what is the ratio $U_1/U_2$?

When the distance between two point charges is increased,the electrostatic potential energy of the system:

If $OP = 1 \, cm$ and $OS = 2 \, cm$,calculate the work done by the electric field in shifting a point charge $q = \frac{4\sqrt{2}}{27} \, \mu C$ from point $P$ to $S$ in the given figure. The dipole moment is $p = 2 \times 10^{-6} \, C \cdot m$.