The distance between the two charges $+q$ and $-q$ of a dipole is $r$. On the axial line at a distance $d$ from the centre of the dipole,the electric field intensity is proportional to:

An electric dipole consists of two opposite charges each of magnitude $1 \,\mu C$ separated by a distance of $2 \,cm$. The dipole is placed in an external field of $10^5 \,N/C$. The maximum torque on the dipole is ......... $Nm$.

Two opposite and equal charges of $4 \times 10^{-8} \ C$ are placed at a distance of $2 \times 10^{-2} \ cm$ to form a dipole. If the dipole is placed in an external electric field of $4 \times 10^8 \ N/C$,calculate the maximum torque and the work done to rotate it by $180^{\circ}$.

Four charges are placed at a distance $a$ from the origin as shown in the figure. The dipole moment of the configuration is:

Match Column-$I$ with Column-$II$ related to an electric dipole of dipole moment $\vec{p}$ that is placed in a uniform electric field $\overrightarrow{E}$.

Column-$I$ (Angle between $\vec{p}$ and $\vec{E}$)	Column-$II$ (Potential energy of the dipole)
$a. 180^{\circ}$	$i. -pE$
$b. 120^{\circ}$	$ii. pE$
$c. 90^{\circ}$	$iii. \frac{1}{2} pE$
	$iv. 0$

Six charges are placed at the vertices of a regular hexagon as shown in the figure. The electric field on the line passing through point $O$ and perpendicular to the plane of the figure at a distance of $x (>> a)$ from $O$ is