Dipole moment is the polarity measurement of a polar covalent bond. The higher the polarity of a molecule the more is the dipole moment. It refers to the molecule which makes a dipole and it is equal to the product of charge on the atoms and the the distance between the two atoms which are bounded with each other. Unit of dipole moment is debye and Standard International Unit of Dipole moment is Coulomb meter. Dipole moments can be calculated through the comparison of dielectric constant and the refractive index of the solutions.
Polar substances existing in the more condensed phases, namely solids and liquids, demonstrate attractive forces due to their small intermolecular radii. These forces are termed, "dipole forces." Polar or polar covalent materials form bonds characterized by the unequal, inter-atomic electron densities that occur due to the localization of the charge. With the net amount of electron density residing on one pole of the atom, this pole will exhibit an overall negative charge. Therefore the opposite pole exhibits an overall positive charge. When the total charges located at the opposing poles are measured & divided by the radius, or distance between the poles, then the observed dipole moment can be calculated. The dipole moment is expressed in units of debeye's (D) and is representative of the overall polarity of the substance, or molecule.