Question

What are dielectrics? Distinguish polar and non polar dielectrics. Define the term Polarization vector.

Answer 1

Polar Dielectrics: Polar dielectrics are those in which the possibility of center coinciding of the positive as well as negative charge is almost zero i.e. they don’t coincide with each other. The reason behind this is their shape. They all are of asymmetric shape. Some of the examples of the polar dielectrics is NH3, HCL, water etc.

Non Polar dielectrics: In case of non polar dielectrics the centres of both positive as well as negative charges coincide. Dipole moment of each molecule in non polar system is zero. All those molecules which belong to this category are symmetric in nature. Examples of non polar dielectrics are: methane , benzene etc.

In classical electromagnetism, polarizationdensity (or electric polarization, or simply polarization) is the vector field that expresses the density of permanent or induced electric dipole moments in a dielectric material.

Answer 2

Answer:

Dielectric Material:

The insulating metarials which are very poor conductor of electric current are called dielectric. Dielectric metarials do not contain free electrons like metal conductors. Here all charges are attached to specific atoms or molecules that's why electrons can't have drift velocity through dielectric. In presence of electric field these charges can only move over microscopic distance within the molecules and significant charge separation is created such that original electric field is cancelled out in dielectric medium.

Non-Polar Dielctric :

In a molecule the protons or positive charges may be imagined to be concentrated in a specific point , this may be called centre of gravity of positive charges.

Simillary there is a centre of gravity of negetive charges or the distributed electrons.

If these two charge centres coincide then the molecule does not possess any intrinsic dipole moment. Such molecules are called Non-Polar Dielectric molecules .

Symmetric molecules like H2, N2, O2, CCl4 nonpolar dielectrics.

Polar Dielectric:

On the other hand, if the two charge centres of a molecule do not coincide but are separated from each other by a small distance, the molecules possess an intrinsic dipole moment (p) and it is called a Polar Dielectric molecules .

Assymetric molecules like H2O, H2S e.t.c are fall into this class.

Polarization Vector (P):

The electric polarization P is defined as the dipole moment per unit volume.

The dimensions of P are charge per unit area hence it can be measured in units of coulomb/meter^2 .