What is the angle between the electric dipole moment and the electric field strength due to it on the equatorial line? $(...^o)$

$A$ system of three charges is placed as shown in the figure. If $D >> d$,the potential energy of the system is best given by:

Two charged particles each of mass $9.8 \text{ g}$ and charges $+20 \mu\text{C}$ and $-20 \mu\text{C}$ are attached to the two ends of a massless and rigid uniform non-conducting rod of length $50 \text{ cm}$. This arrangement is held in a uniform electric field of $12.1 \text{ N/C}$,such that the rod makes a very small angle with the field direction. If the rod is set free,the minimum time needed for the rod to become parallel to the direction of the electric field is ................ seconds.

Three point charges $q, -2q$ and $q$ are placed along the $x$-axis at $x = -a, 0$ and $a$ respectively. As $a \rightarrow 0$ and $q \rightarrow \infty$ while $qa^2 = Q$ remains finite,the electric field at a point $P$,at a distance $x$ $(x \gg a)$ from $x = 0$ is $E = \frac{\alpha Q}{4 \pi \epsilon_0 x^\beta} \hat{i}$. Then:

$A$ dipole is placed in a uniform electric field,its potential energy will be minimum when the angle between its axis and field is

An electric dipole placed in a uniform electric field experiences maximum torque when the dipole is placed: