Dielectrics are insulators that get polarized when an electrical field is applied.
- Polar molecules inside the material orientate in the direction of an externally applied field like tiny dipoles ![[Pasted image 20240306145340.png]]
- Non-polar molecules can also become dipoles. Electrons in dielectric materials are bound to the nucleus and thus present very little movement. However, when external voltage is applied, the nucleus and the atoms get attracted to negative and positive sides respectively. These are called bound charges in contrast to free charges.
Examples: Ceramics, mica, and certain type of plastics are examples of dielectric materials.
#Permittivity and Susceptibility
The dielectric material is characterized by its permittivity $\epsilon$ (same units as $\epsilon_{0}$)
$$ \epsilon=\epsilon_{r} \epsilon_{0} $$ Permittivity can be understood as the ability of a material to resist the formation of electric fields inside. $\epsilon_{r}$ is the relative permittivity (no units). Equivalently, we define the electric susceptibility $\chi_{\mathrm{e}}$ $$ \varepsilon_{\mathrm{r}}=1+\chi_{\mathrm{e}} $$| Material | $\varepsilon_r$ |
|---|---|
| Vacuum | $1$ |
| Air | $1.0059$ |
| Teflon | $2.1$ |
| Mica | $3-6$ |
| Plexiglas | $3.40$ |
| Glass | $5-10$ |
| Glycerin | $42.5$ |
| Water | $80.4$ |
Capacitors