Describing material media
Introduction
The material media are described by using of material regions:
- mainly volume regions in 3D; surface regions and line regions are also possible in 3D
- mainly surface regions in 2D problems; line regions and point regions are also possible in 2D
For additional information about the role of the regions, see chapter Physics: principles.
Material regions: overview
Volume, surface or line material regions enable the modeling of the material media (with materials). The physical properties of the medium are those of the corresponding material region.
| A region… | enables the modeling… |
|---|---|
| air or vacuum |
of air or of a vacuum (relative permittivity εr = 1) |
| perfect conductor* |
of a medium of perfect conductor: equipotential frontier (floating or fixed value of electric potential) with a normal electric field |
|
dielectric (+ electric charge sources q) |
of a dielectric medium (relative permittivity εr) with a possible volume density of the electric charge source (uniform or space dependent) |
Thin regions (3D)
Thin regions enable the modeling of regions of slight thickness, for example cracks in the dielectric of a capacitor, etc.
In 3D problems for a thin dielectric region, the direction of the electric field can be selected by the user, as indicated in the table below.
| Thin region | Direction of fields E and D | |
|---|---|---|
| no restriction | quasi tangential | |
|
dielectric (+ electric charge sources q) |
thin region with random ε permittivity |
thin region with: ε2 >> ε1
|
Filiform regions (3D)
Filiform regions enable the modeling of small cross-section regions.
In 3D problems for a filiform dielectric region, the direction of the electric field is imposed by Flux. The electric field is considered tangent to the line that models the filiform region.