Question

What is meant by electric susceptibility?

Answer 1

Electric susceptibility, often denoted as \( \chi_e \), is a measure of how easily a material can become polarized when exposed to an electric field. In simpler terms, it tells us how much a material's electric properties change in response to an external electric field.

When an electric field is applied to a material, the charges inside the material rearrange slightly, creating a small internal electric field that opposes the applied one. The extent to which the material polarizes (or rearranges its charges) depends on the material's electric susceptibility.

### Formula:
The relationship between the electric field \( \mathbf{E} \) and the polarization \( \mathbf{P} \) of the material is given by:
\[
\mathbf{P} = \varepsilon_0 \chi_e \mathbf{E}
\]
where:
- \( \mathbf{P} \) is the polarization of the material,
- \( \varepsilon_0 \) is the permittivity of free space,
- \( \chi_e \) is the electric susceptibility,
- \( \mathbf{E} \) is the applied electric field.

### Key points:
- Materials with a high electric susceptibility are easily polarized by an electric field.
- If the material has \( \chi_e > 0 \), it is considered a **dielectric material** (insulator) that can be polarized.
- If \( \chi_e < 0 \), the material is called a **paramagnetic material** (which typically weakly opposes polarization).

Electric susceptibility helps us understand how materials react in electric fields, which is important in designing capacitors, insulators, and other electronic components.