What is electric dipole?Why do we assume the electric dipole to be small in size in most of the cases?

Explanation

A system of two equal and opposite charges placed at some separation is called electric dipole. The concept of electric dipole is useful at a molecular level and that is why we refor small dipole as an ideal dipole. In some molecules, the centre of positive charge gets shifted from the centre of negative charge. Such a molecule behaves like one electric dipole.