Dielectrics – Polar and Non-Polar Dielectrics
Dielectrics are insulating (non-conducting) substances which transmits electric effect without conducting. It has no free electrons.
There are two types of dielectrics –
1. Polar dielectrics: Like water, alcohol, CO2, NH3, HCL. etc are made of polar atoms/molecules.
A polar molecule has permanent electric dipole moment in the absence of electric field also. But a polar dielectric has net dipole moment zero in the absence of electric field because polar molecules are randomly oriented.
In the presence of electric field polar molecules trends to line up in the direction of electric field, and the substances has finite dipole moment.
If Eext is the external field applied and Ein is the field due to alignment of dipoles.
2. Non polar dielectrics: Like N2, O2, Benzene, Methane, etc are made of non-polar atoms/molecules.
In non-polar molecules, when no electric field is applied the centre of positive charge coincides with the centre of negative charge in the molecule. Each molecule has zero dipole moment in its normal state.
When electric field is applied, positive charge experiences a force in the direction of electric field and negative charge experiences a force in the direction opposite to the field i.e. molecules becomes included electric-dipole.
If Eext is the external field applied and Eind is the field induced.