An electric dipole is placed in a non-uniform electric field,then . . . . . . .

As shown in the figure,a charge $+q$ is moved from point $A \,(r, 135^{\circ})$ to point $B \,(r, 45^{\circ})$. If the dipole moment is $p$,what is the work done by an external agent?

An electric dipole of dipole moment $P$ is placed parallel to a uniform electric field of intensity $E$. On rotating it through an angle of $90^\circ$ from this position, the amount of work done is . . . . . . .

There exists a non-uniform electric field along the $x-$ axis as shown in the figure below. The field increases at a uniform rate along the $+ve$ $x-$ axis. $A$ dipole is placed inside the field as shown. Which one of the following is correct for the dipole?

For the shown situation of two dipoles,the nature of forces between them is:

Two small spherical balls of mass $10 \ g$ each with charges $-2 \ \mu C$ and $2 \ \mu C$,are attached to two ends of a very light rigid rod of length $20 \ cm$. The arrangement is now placed near an infinite nonconducting charge sheet with a uniform charge density of $100 \ \mu C / m^2$ such that the length of the rod makes an angle of $30^{\circ}$ with the electric field generated by the charge sheet. The net torque acting on the rod is (Take $\varepsilon_0 = 8.85 \times 10^{-12} \ C^2 / Nm^2$) (in $Nm$)