An electric dipole is formed by placing a charge of $4 \times 10^{-8} \ C$ at a distance of $2 \times 10^{-2} \ cm$. If it is placed in an electric field of $4 \times 10^8 \ N/C$,what is the maximum torque acting on it and the work done to rotate the dipole by $180^{\circ}$?

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?

Two parallel disks each having radius $R$ are separated by a distance $l$. The surface charge densities are $\sigma$ and $-\sigma$. The electric field at point $P$,a large distance $r$ along the axis of the disks is:

Two short dipoles $A$ and $B$, $A$ having charges $\pm 2 \mu C$ and length $1 \text{ cm}$, and $B$ having charges $\pm 4 \mu C$ and length $1 \text{ cm}$, are placed with their centres $80 \text{ cm}$ apart as shown in the figure. The electric field at a point $P$, equidistant from the centres of both dipoles, is . . . . . . $\text{N/C}$.

Two charges $+q$ and $-q$ are kept at a certain distance apart. Then, at any point on the right bisector of the line joining the two charges:

An electric dipole is situated in an electric field as shown in the figure. The dipole and electric field are both in the plane of the paper. The dipole is rotated about an axis perpendicular to the paper at point $A$ in an anti-clockwise direction. If the angle of rotation is measured with respect to the direction of the electric field,then the torque for different values of the angle of rotation $\theta$ is correctly represented by which graph among $a, b, c, d$ given in the figure?