A charge $q={10}^{-6}C$ of mass $2 \mathrm{g}$ (fig.) is free to move when released at a distance '$a$' from the fixed charge $\mathrm{Q}$. Calculate its speed, when it recedes to a distance $b$:

 

[Assume $a=1 m, b=10 m, Q={10}^{-3} C$]

There is a uniform electric field of strength ${10}^3 \mathrm{V} {\mathrm{m}}^{-1}$ along $y$-axis. A body of mass $1 \mathrm{g}$ and charge ${10}^{-6} \mathrm{C}$ is projected into the field from origin along the positive $x$-axis with a velocity $10 \mathrm{m} {\mathrm{s}}^{-1}$. Its speed in $\mathrm{m} {\mathrm{s}}^{-1}$ after $10 \mathrm{s}$ is (neglect gravitation)

The adjacent diagram shows a charge $+Q$ held on an insulating support $S$ and enclosed by a hollow spherical conductor. $O$ represents the centre of the spherical conductor and $P$ is a point such that $OP=x$ and $SP=r$. The electric field at point $P$ will be:

Consider the following statements about electric dipole and select the correct ones.

S1: Electric dipole moment vector $\overrightarrow{p}$ is directed from negative charge to positive charge.

S2: The electric field of a dipole at a point with position vector $\overrightarrow{r}$ depends on $\left|\overrightarrow{r}\right|$ as well as the angle between $\overrightarrow{r}$ and $\overrightarrow{p}$.

S3: The electric dipole potential falls off as $\frac{1}{r^2}$ and not as $\frac{1}{r}$.

S4: In a uniform electric field, the electric dipole experiences no net forces but a torque $\overrightarrow{\tau }=\overrightarrow{p}\times \overrightarrow{E}$.