Question

What is the physical significance of electric susceptibility?

Answer 1

Electric susceptibility (\(\chi_e\)) is a measure of how easily a material can become polarized in response to an applied electric field. It tells us how much the material’s electric dipole moment will increase when the external electric field is applied.

Here's the physical significance of electric susceptibility:

1. Response to Electric Field: The electric susceptibility indicates how much a material will be polarized (develop electric dipoles) when subjected to an external electric field. The larger the value of susceptibility, the greater the polarization for a given field.
   

1. Polarization of Materials: Materials with high susceptibility tend to get polarized more easily, meaning their individual atoms or molecules align with the electric field more effectively. On the other hand, materials with low susceptibility are less responsive to the field.
   

1. Relation to Permittivity: The electric susceptibility is related to the permittivity (\(\varepsilon\)) of the material. The permittivity of a material (\(\varepsilon\)) is the material's ability to permit the formation of an electric field within it, and it's given by the formula:
   

   \[
   \varepsilon = \varepsilon_0 (1 + \chi_e)
   \]
   where \(\varepsilon_0\) is the permittivity of free space. A high susceptibility increases the permittivity, meaning the material can store more electric energy for a given applied field.

1. Behavior in Different Materials:
   

   - Dielectrics (Non-conductors): Materials with positive susceptibility (like glass, rubber, or air) are dielectrics. They get polarized when an electric field is applied, which enhances the field inside them.
   - Conductors: In conductors, free charges can move easily, so the electric field inside a conductor is generally zero (except near the surface), making the concept of susceptibility less relevant in this case.

In summary, electric susceptibility helps to describe how a material reacts to an electric field in terms of polarization and how much it "resists" or "supports" the field.