The Current Conservation node adds the continuity equation for the electrical potential and provides an interface for defining the electric conductivity as well as the constitutive relation and the relative permittivity for the displacement current.

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.

See Electric Field as described for the Charge Conservation node for the Electrostatics interface.

By default, the Electrical conductivity σ (SI unit: S/m) for the media is defined From material. Or select User defined, Linearized resistivity, Effective medium, or Archie’s law.

For User defined select Isotropic, Diagonal, Symmetric, or Anisotropic depending on the characteristics of the electrical conductivity, and then enter values or expressions in the field or matrix.

Select Linearized resistivity for a temperature-dependent conductivity (this occurs in, for example, Joule heating, and is also called resistive heating). The equation describing the conductivity:

where ρ0 is the resistivity at the reference temperature T0, and α is the temperature coefficient of resistance, which describes how the resistivity varies with temperature.

The default Reference temperature Tref (SI unit: K), Resistivity temperature coefficient α (SI unit: 1/K), and Reference resistivity ρ0 (SI unit: Ω⋅m) are taken From material, which means that the values are taken from the domain material.

To specify other values for any of these properties, select User defined from the list and then enter a value or expression. T is the current temperature, which can be a value that is specified as a model input or the temperature from a Heat Transfer interface. The definition of the temperature field appears in the Model Inputs section.

When Effective medium is selected, the Effective Medium subnode is available from the context menu (right-click the parent node) or from the Physics toolbar, Attributes menu. When Archie’s law is selected, an Archie’s Law subnode is available.