### 1.2.16. Electric Field

There are 2 options for the modeling of electric field effects:

- The `Electric Potential` option is formulated for conductive media only and it assumes a quasi-steady field. Other quantities of interest are derived from it such as `Electric Potential`, `Electric Field`, `Current Density`, and `Joule heating`.

- The `User Defined` option can be used to directly specify an externally imposed electric field. This option does not require any boundary conditions.

If an electric model is active in combination with other models, it may have some direct influence on those models as well. For example:

- If the magnetic model is also active, and the material is conductive, the Lorentz force is added to the momentum equations. For details, see Magnetohydrodynamics (MHD) in the CFX-Solver Theory Guide.

- If the model includes heat transfer, the Joule heating quantity is automatically added to the energy equation and is defined by:

  | (1–16)

For multiphase flows, the electric surface current at the interface between the phases is ignored and a volume fraction weighted electrical conductivity is used.

Electric fields can be specified at boundaries when the `Electric Potential` model has been activated for a domain. For details, see Electromagnetic Model. The following options are available:

- `Voltage`

  Specifies the Voltage at the boundary.

- `Ground`

  Equivalent to `Voltage` with a Voltage equal to `0`.

- `Flux in`

  Specifies the Electric Current at the boundary according to the equation:

  | (1–17)

  Where is the normal component of the electric current density at the boundary with incoming electric current being positive.

- `Zero Flux`

  Equivalent to `Flux in` with equal to `0`.

- `Electric Current Transfer Coefficient`

  This boundary condition can be used to model an additional electric resistance by the equation:

  | (1–18)

  The Transfer Coefficient could be interpreted as a thin material of electrical conductivity, , and of finite thickness, , such that:

  | (1–19)

- `Conservative Interface Flux`

  This boundary condition is used at domain interfaces to indicate that the electric current will flow between the current boundary towards the other side of the interface. This means, that a similar `Conservative Interface Flux` option must be specified on the boundaries on the other side of the interface.

- `Electric Field Contact Resistance`

  This model represents an electric resistance between two sides of a domain interface.

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