Write the definition of electric dipole moment.

Hint: A pair of equal and opposite charges (i.e. +q and -q) separated by a certain distance is known as an electric dipole. The centre of the electric dipole is the midpoint of the system of two charges which is referred to as electric dipole. The electric dipole moment is used to find the direction of the source of electric field in the electric dipole.

Complete step by step answer:
Electric dipole moment: It may be defined as the product of magnitude of separation of equal and opposite charges (either charge) in a system through a small distance. It is a vector quantity. Its direction is from negative charge to positive charge.

Mathematically, it is represented by $p$ and is equal to –
$p = q \times d$
In vector form,
$\overrightarrow{p}=q\times \overrightarrow{d}$
Where q is the magnitude of either charge and d is the distance between the two equal and opposite charges.
SI unit of electric dipole moment is C-m (coulomb-meter). Its other unit is Ampere-second.

Additional Information:
It is a useful concept in atoms and molecules where the effects of charge separation are measurable, but the distances between the charges are too small to be easily measurable. It is also a useful concept in dielectrics and other applications in solid and liquid materials.

Note: Physically, the electric dipole moment represents the polarity of a system of charges. More the dipole moment more will be the polarity and vice-versa. The electric dipole is always directed towards the source charge. The direction of electric dipole moment always points towards the source of electric field in the system.