Question

In which orientation, a dipole placed in a uniform electric field is in
(i) stable equilibrium and
(ii) unstable equilibrium?

Answer 1

Hint: The electric dipole moment is a vector quantity; it has a characterized direction which is from the negative charge to the positive charge. However, it is important to remember that the course of direction is just continued in Physics. In Chemistry, the convention is taken to be inverse for example from positive to negative. The line along the direction of an electric dipole is known as the axis of the dipole.

Complete answer:
Here we will first know the concept of electric dipole and that we will know when the dipole will be stable equilibrium and unstable equilibrium.A pair of opposite charges q and –q separated by a distance d is called an electric dipole. Electric dipoles in space often point from negative charge -q to positive charge q by default.

The dipole's centre is defined as the point where q and –q meet a pair of electric charges of two opposite signs and equal magnitude separated by distance is the simplest example of an electric dipole. The electric dipole is important in both electrostatics and chemistry. Since the centres of positive and negative charges in most molecules converge at the same location, the difference between two charges is zero.

Carbon dioxide and methane belong to the zero dipole moment group. Non-polar molecules are the name for this type of molecule. Polar molecules are those which have a permanent dipole moment since the centres of positive and negative charge do not coincide.
-The dipole is in stable equilibrium when it is aligned parallel to the electric field (i.e. the angle between the dipole moment and the electric field is $0{}^{\circ }$).
-The dipole is in unstable equilibrium when it is oriented anti-parallel to the electric field (i.e. the angle between the dipole moment and the electric field is $180{}^{\circ }$).

Note: Assume that a dipole is formed by two charges, –q at A and +q at B, separated by a distance r. Assume that AB's midpoint is O. When the angle between dipole moment and the electric field is $90{}^{\circ }$, then the Electric potential due to a dipole at any point P, such that OP=r will be zero, according to $V={\displaystyle \frac{1}{4\pi \epsilon }}{\displaystyle \frac{p\cos \theta }{r^2}}$.