The distance between charges $+q$ and $-q$ is $2l$ and between $+2q$ and $-2q$ is $4l$. The electrostatic potential at point $P$ at a distance $r$ from centre $O$ is $-\alpha \left[ \frac{ql}{r^2} \right] \times 10^9 \text{ V}$,where the value of $\alpha$ is . . . . . . . (Use $\frac{1}{4\pi\varepsilon_0} = 9 \times 10^9 \text{ Nm}^2\text{C}^{-2}$)

The force of interaction between two co-axial short electric dipoles whose centers are $R$ distance apart varies as:

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: If an electric dipole of dipole moment $30 \times 10^{-5} \, Cm$ is enclosed by a closed surface,the net flux coming out of the surface will be zero.
Reason $R$: An electric dipole consists of two equal and opposite charges.
In the light of the above statements,choose the correct answer from the options given below:

An electric dipole of dipole moment $p$ is aligned parallel to a uniform electric field $E$. The energy required to rotate the dipole by $90^{\circ}$ is $\left[\begin{array}{ll}\sin 0^{\circ}=0, & \sin 90^{\circ}=1 \\ \cos 0^{\circ}=1, & \cos 90^{\circ}=0\end{array}\right]$

For an electric dipole, if the magnitude of each charge is $10^{-10} \, \text{stC}$ and the distance between them is $1 \, \mathring{A}$, then the dipole moment is:

What is a point dipole?