Charge Conservation
The Charge Conservation node adds the equations for charge conservation according to Gauss’ law for the electric displacement field. It provides an interface for defining the constitutive relation and its associated properties such as the relative permittivity.
Material Type
The Material type setting decides how materials behave and how material properties are interpreted when the mesh is deformed. Select Solid for materials whose properties change as functions of material strain, material orientation, and other variables evaluated in a material reference configuration (material frame). Select Non-solid for materials whose properties are defined only as functions of the current local state at each point in the spatial frame, and for which no unique material reference configuration can be defined. Select From material to pick up the corresponding setting from the domain material on each domain.
Electric Field
Select a Constitutive relation to describe the macroscopic properties of the medium (relating the electric displacement D with the electric field E) and the applicable material properties, such as the relative permittivity. Select:
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Relative permittivity (the default) to use the constitutive relation D = ε0εrE. Then the default is to take the Relative permittivity εr (dimensionless) values From material.  For User defined, select Isotropic, Diagonal, Symmetric, or Anisotropic and enter values or expressions in the field or matrix. The default is 1. If Effective medium is selected, the Effective Medium subnode is available from the context menu (right-click the parent node) as well as from the Physics toolbar, Attributes menu.
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Polarization to use the constitutive relation D = ε0E + P. Then enter the components based on space dimension for the Polarization vector P (SI unit: C/m2). The defaults are 0 C/m2.
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Remanent electric displacement to use constitutive relation D = ε0εrE + Dr, where Dr is the remanent displacement (the displacement when no electric field is present). Then the default is to take the Relative permittivity εr (dimensionless) values From material.  For User defined, select Isotropic, Diagonal, Symmetric, or Anisotropic and enter values or expressions in the field or matrix. Then enter the components based on space dimension for the Remanent electric displacement Dr (SI unit: C/m2). The defaults are 0 C/m2.