Dielectric Materials | What Are Dielectric Materials
Dielectric Materials | What Are Dielectric Materials :- Insulators which, when placed in an external electric field, undergo a minute local displacement of charges are called dielectric materials. Dielectrics behave as insulators up to a certain maximum value of the electric field; however, if the magnitude of the electric field exceeds this definite value, they begin to lose their insulating property and start conducting.
Dielectric Strength of Dielectric Materials
The maximum value of the electric field that a dielectric can withstand without undergoing breakdown and while retaining its insulating property is called dielectric strength.
Its units are volt per meter (V/m) and its dimensions are [MLT-3A-1].
Types of Dielectric Materials
Dielectric materials are of two types :
(i) Polar dielectrics and
(ii) Non-polar dielectrics.
(i) Polar Dielectric
In the absence of an external electric field, in these dielectrics the centers of positive and negative charges do not coincide due to the asymmetric shape of the molecules. Each molecule therefore possesses its own permanent electric dipole moment. However, since these dipoles are randomly oriented, the average dipole moment per unit volume is zero in the absence of an external electric field.
In the presence of an external electric field, these dipoles try to align themselves in the direction of the electric field.
Examples: Water, alcohol, CO2, HCl, NH3
(ii) Non-Polar Dielectric
Non-polar dielectric materials are those in which, due to the symmetrical structure of their molecules or atoms, the centers of positive and negative charges coincide. Therefore, in the absence of an external electric field, their net electric dipole moment is zero. However, when an external electric field is applied, the charge distribution within the molecules gets slightly distorted, and an induced electric dipole moment is produced.
Examples of non-polar dielectric materials include nitrogen, oxygen, benzene, and methane.