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 .......

Three point charges of $2 \ mC$ each are kept at the vertices of an equilateral triangle of side $50 \ cm$. If the system is supplied energy at the rate of $2 \ kW$,the time taken to move one of the charges to the midpoint of the line joining the other two charges is (in $s$)

An electric dipole with dipole moment $p$ is placed in an electric field of intensity $E$. Initially,the dipole is parallel to the field. What is the work done by an external agent to rotate the dipole by $180^{\circ}$ in the electric field?

Write an equation for the electric potential due to an electric dipole and state its important features. Discuss its special cases.

An electric dipole of moment $p$ is placed in the position of stable equilibrium in a uniform electric field of intensity $E$. It is rotated through an angle $\theta$ from the initial position. The potential energy of the electric dipole in the final position is

The work done in rotating a dipole placed parallel to the electric field through $180^{\circ}$ is $w$. What is the work done in rotating it through $60^{\circ}$? $(\cos 0^{\circ}=1, \cos 60^{\circ}=\frac{1}{2}, \cos 180^{\circ}=-1)$