The relation between the intensity of the electric field of an electric dipole at a distance $r$ from its centre on its axis and the distance $r$ is . . . . . . . (where $r \gg 2a$)

Two charges $+q$ and $-q$ are placed at a distance $b$ apart as shown in the figure. The electric field at a point $P$ on the perpendicular bisector as shown is

$A$ wheel of mass $m$ has charges $+q$ and $-q$ at diametrically opposite points. It remains in equilibrium on a rough inclined plane of inclination $\theta$ in the presence of a uniform horizontal electric field $E$. Find the value of $E$.

An electric dipole of moment $\vec{P}$ is lying along a uniform electric field $\vec{E}$. The work done in rotating the dipole through $\frac{\pi}{3}$ radians is:

Which of the following molecules is a polar molecule?

An electric dipole has a fixed dipole moment $\vec{P}$ which makes an angle $\theta$ with respect to the $x$-axis. When subjected to an electric field $\vec{E_1} = E\hat{i}$,it experiences a torque $\vec{T_1} = \tau\hat{k}$. When subjected to another electric field $\vec{E_2} = \sqrt{3}E\hat{j}$,it experiences a torque $\vec{T_2} = -\vec{T_1}$. The angle $\theta$ is .......$^o$.