An electric dipole of moment $\overrightarrow{p}$ is lying along a uniform electric field $\overrightarrow{E}$. The work done in rotating the dipole through $90^{\circ}$ is $\left[\sin 0^{\circ}=\cos 90^{\circ}=0, \cos 0^{\circ}=\sin 90^{\circ}=1\right]$

Two negative charges,each of magnitude $q$,are separated by a distance of $2r$. $A$ positive charge $q$ is placed at their center. The potential energy of the system is $U_1$. If the two negative charges are interchanged with the positive charge such that the new potential energy is $U_2$,what is the ratio $U_1/U_2$?

When a dipole placed parallel to electric field is rotated through $\pi^c$, the work done is $W$. The work done in rotating the dipole through $(\frac{\pi}{3})^c$ is $(\cos 0^\circ = 1, \cos 60^\circ = \frac{1}{2}, \cos 180^\circ = -1)$

The electric potential at a distance of $3 \, m$ on the axis of a short dipole of dipole moment $4 \times 10^{-12} \, C \cdot m$ is ......... $mV$.

Three charges $Q$,$(-2q)$ and $(-2q)$ are placed at the vertices of an isosceles right-angled triangle as shown in the figure. The net electrostatic potential energy is zero if $Q$ is equal to

Three point charges $Q$, $+2q$ and $+q$ are placed at the vertices of a right-angled isosceles triangle of side length $\sqrt{2}a$. The net electrostatic potential energy of the configuration is zero, if $Q$ is equal to