Consider the configuration of a system of four charges each of value $+q$. The work done by an external agent in changing the configuration of the system from Figure $(1)$ to Figure $(2)$ is:

$A$ dipole having dipole moment $p$ is placed in front of a solid uncharged conducting sphere as shown in the diagram. The net potential at point $A$ lying on the surface of the sphere is :-

Two charges $5 \text{ nC}$ and $-2 \text{ nC}$ are placed at points $(5 \text{ cm}, 0, 0)$ and $(23 \text{ cm}, 0, 0)$ in a region of space where there is no other external field. The electrostatic potential energy of this charge system is

Three point charges $+Q$,$+2q$,and $+q$ are placed at the vertices of a right-angled isosceles triangle as shown in the figure. The net electrostatic potential energy of the configuration is zero,if $Q$ is equal to

Derive the expression for the potential energy of an electric dipole in a uniform electric field.

$A$ molecule of a substance has a permanent electric dipole moment of magnitude $10^{-29} \; C \; m$. $A$ mole of this substance is polarized (at low temperature) by applying a strong electrostatic field of magnitude $10^{6} \; V \; m^{-1}$. The direction of the field is suddenly changed by an angle of $60^{\circ}$. Estimate the heat released (in $J$) by the substance in aligning its dipoles along the new direction of the field. For simplicity,assume $100 \%$ polarization of the sample.