Question

What is the term polarization of a dielectric and write its relation with susceptibility?

Answer 1

Polarization of a Dielectric:

Polarization refers to the process in which the positive and negative charges within a dielectric material (an insulating material) shift slightly when an external electric field is applied. This shift doesn’t involve the charges moving freely (as in conductors), but rather a small displacement of the positive and negative charge centers. The result is that the material develops a dipole moment, meaning there is a separation of charges within the material.

In simple terms, when a dielectric is placed in an electric field, it gets polarized because the electric field makes the tiny charges inside it shift slightly, aligning themselves with the field.

Types of Polarization:

1. Electronic polarization: Displacement of electron cloud relative to the nucleus.
   

1. Ionic polarization: Displacement of ions within the material.
   

1. Orientation polarization: Alignment of permanent dipoles in the material with the external field.
   

Relation with Susceptibility (χ):

The polarization (\( \mathbf{P} \)) of a dielectric material is related to the applied electric field (\( \mathbf{E} \)) through the material's electric susceptibility (\( \chi_e \)).

Mathematically, this is given by:

\[
\mathbf{P} = \epsilon_0 \chi_e \mathbf{E}
\]

Where:

1. \( \mathbf{P} \) is the polarization vector (C/m²),
   

1. \( \epsilon_0 \) is the permittivity of free space (8.854 × 10⁻¹² C²/N·m²),
   

1. \( \chi_e \) is the electric susceptibility (a dimensionless quantity),
   

1. \( \mathbf{E} \) is the applied electric field (V/m).
   

Key Points:

1. Susceptibility (\( \chi_e \)) measures how easily a material becomes polarized in response to an electric field. Higher susceptibility means the material is more easily polarized.
   

1. The polarization increases with the electric field, and the susceptibility tells you the extent to which this happens.
   

So, the polarization depends directly on both the applied electric field and the material's susceptibility.