An electric dipole has the magnitude of its charge as $q$ and its dipole moment is $p$. It is placed in a uniform electric field $E$. If its dipole moment is along the direction of the field, the force on it and its potential energy are respectively

When is an electric dipole in a stable equilibrium in a uniform electric field.

Three charges $+2q, -q$ are $\mathit{-}q$  are placed at the vertices $A, B$ and $C$ respectively of an equilateral triangle $ABC$ of side $a$. Find the magnitude of dipole moment of this system.

Demonstrate that the potential of the field generated by a dipole, with electric moment $\overrightarrow{\mathit{P}}$, may be represented as $\mathrm{\phi }=\frac{\overrightarrow{p}·\overrightarrow{r}}{4\mathrm{\pi }{\epsilon }_0{r}^3}$, where $\overrightarrow{\mathit{r}}$ is the radius vector. Using this expression, find the magnitude of the electric field strength vector as a function of $r$ and $\mathrm{\theta }$.