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Monday, December 23, 2019

Dielectrics - Polar, Non Polar, uses

A dielectric is a non conducting substance introduced between the plates of a capacitor.

What is Non Polar Dielectric?


This is a substance in which the net electric dipole moment is zero because of its symmetrical structure. In this the center of gravity of positive charges and  center of gravity of negative charges
will coincide.

What is Polar Dielectric?

Because of their non symmetrical structure these dielectrics have permanent dipole moment. In this there are permanent electric dipoles present. On this if an external electric field is applied, torque acts on these dipoles rotating them in direction of applied electric field. When an external electric field is applied on non polar dielectric this dielectric gets polarized forming induced charges on the surfaces.      

Uses of Dielectric


1. It maintains mechanical separation between the plates.

2. It decreases the field as well as potential but increases the capacity

3.  Increases capacitance between metal plates
When a non polar dielectric is introduced between the plates it is leading to the displacement of negative charges in the dielectric. Because of the displacement of negative charges, the center of gravity of negative charges is not coinciding the center of gravity of positive charges, thus forming dipoles. This phenomenon of formation of electric dipoles when an external electric field is applied on a non-polar dielectric is known as Polarisation. 

Therefore, induced charges are appearing on the surfaces of dielectric forming their own electric field  Eᵢ. This Eᵢ opposes original electric field Eₒ, thus net electric field E is decreasing.

E=Eₒ-Eᵢ

Therefore, potential between the plates is also decreasing resulting in increase in capacitance.

4. Used for withstanding high potentials
 Any dielectric can withstand a maximum electric field before becoming a partial conductor. This maximum electric field, a dielectric can withstand before reaching breakdown condition is known as dielectric strength of dielectric.
Therefore, heavy capacitors use dielectrics using highest dielectric strengths to withstand large potentials. 
 

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