An electric dipole is placed in a non uniform electric field, then it experiences:

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 $\overrightarrow{\tau }=\overrightarrow{p}\times \overrightarrow{E}$.

Two point charges $a$ & $b$ whose magnitudes are same are positioned at a certain distance from each other; $a$ is at origin. Graph is drawn between electric field strength $E$ and distance x from $a$. $E$ is taken positive if it is along the line joining from $a$ to $b$

From the graph it can be decided that.

A circular disc of radius $4\mathrm{cm}$ with charge density $10 \mathrm{nC}/{\mathrm{m}}^2$ is placed in $Y-Z$ plane with center at $z=0$. Find electric field at a distance of $3\mathrm{cm}$ perpendicular to plane of disc.