Dielectrics are the materials which do not contain free charges for conduction.
Thus, dielectrics are basically insulators as insulators do not conduct electricity through them. But, dielectrics, contain positive and negative charges which are bounded together and these charges could be effected by
the electric field. The main function of dielectric is the charge storage.
POLAR AND NON-POLAR DIELECTRICS
An atom contains a positive charge in the nucleus and negative charge (electrons) orbitting around the nucleus. The positive as well as the negative charges can be considered to be concentrated at a point. The point at which the positive charge can be assumed to be concentrated is termed as the centre of gravity of the positive charge. Similarly, the point at which the negative charge can be assumed to be concentrated is termed as the centre of gravity of the negative charge. Now we can define the polar and non-polar dielectrics as :
Polar Dielectrics or Molecules: If the centre of gravity of the positive charges and negative charges are separated by a finite distance (10-10m), then the dielectric is called polar dielectric (Refer Figure).
Figure: A polar dielectric
Example. Water, CO2 NH 3 etc.
Thus, polar moleculer or dielectrics have permanent dipole moment.
Note 1: After reading this article, you will be able to answer the following questions:
What are dielectric materials or substances,
Define dielectric materials,
Name the types of dielectric materials,
Classify the dielectric materials,
What are polar dielectrics,
What are polar molecules,
Write the examples of dielectric materials,
Why polar molecules have permanent dipole moment
Note 2. In the next article, I will discuss non-polar dielectrics.