Formula: Polarization of a Material
$$\class{red}{P} ~=~ \class{green}{\chi_{\text e}} \, \varepsilon_0 \, \class{purple}{E}$$
$$\class{red}{P} ~=~ \class{green}{\chi_{\text e}} \, \varepsilon_0 \, \class{purple}{E}$$
$$\class{purple}{E} ~=~\frac{ \class{red}{P} }{ \class{green}{\chi_{\text e}} \, \varepsilon_0 }$$
$$\class{green}{\chi_{\text e}} ~=~\frac{ \class{red}{P} }{ \class{purple}{E} \, \varepsilon_0 }$$
Polarization
$$ \class{red}{\boldsymbol P} $$ Unit $$ \frac{ \mathrm C }{ \mathrm{m}^2 } $$Polarization describes the density of electric dipoles in a material (number per volume) and induces a polarization field \( \class{purple}{E_{\text{p}}} \), which can be aligned either opposite or in the same direction as the external electric field, thereby amplifying or weakening the external electric field.
Electric field (E field)
$$ \class{purple}{\boldsymbol E} $$ Unit $$ \frac{\mathrm{V}}{\mathrm{m}} = \frac{\mathrm{N}}{\mathrm{C}} = \frac{\mathrm{kg} \, \mathrm{m}}{\mathrm{A} \, \mathrm{s}^3} $$
External electric field in which the dielectric material is situated.
Electric susceptibility
$$ \class{green}{\chi_{\text e}} $$ Unit $$ - $$Electric susceptibility indicates how well a material can be polarized by an external electric field \( \class{purple}{E} \). In other words, it quantifies how effectively the external electric field is weakened or strengthened within the material.
- For \( \class{green}{\chi_{\text{e}}} > 0 \), the external electric field is amplified within the material.
- For \( \class{green}{\chi_{\text{e}}} < 0 \), the external electric field is weakened within the material.
- For \( \class{green}{\chi_{\text{e}}} = 0 \), it is neither weakened nor strengthened. The "material" is vacuum.
| Material | Electric susceptibility |
|---|---|
| Vacuum | 0 |
| Air (0°C) | 0.0005 |
| Glass | 4 bis 9 |
| Water (0°C) | 87 |
| Water (40°C) | 72.4 |
| Ice (-20°C) | 15 |
| Hydrogen Cyanide | 94 |
| Ethanol (20°C) | 24.8 |