6.5 Orientational, ionic and electronic polarizations

When an electric field is applied on a dielectric crystal, then the positive charges of atoms and molecules are displaced along the field while the negative charges in a direction opposite to that of the applied field. This is the basis for polarization of a dielectric substance.

If a molecule has permanent dipole moment, then it is a dipolar molecule and the substance is a dipolar substance. Example is H2O molecule. In the absence of an external electric field, the dipoles are randomly oriented, so that polarization is zero. But when the electric field is applied, these dipoles tend to rotate different extents in the direction of an applied electric field giving rise to dipolar or orientational ...

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