FEM EquationElectricforce

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    FEM EquationElectricforce.svg FEM EquationElectricforce

    Menu location
    Solve → Electromagnetic Equations → Electricforce equation
    Default shortcut
    Introduced in version
    See also
    FEM Electrostatic equation


    This equation describes the electrostatic force acting on a surface.

    For info about the math of the equation, see the Elmer models manual, section Electrostatic force.


    1. After adding an Elmer solver as described here, select it in the tree view.
    2. Either use the toolbar button FEM EquationElectricforce.svg or the menu Solve → Electromagnetic Equations → Electricforce equation.
    3. Now either use the toolbar button FEM EquationElectrostatic.svg or the menu Solve → Electromagnetic Equations → Electrostatic equation. This is important because the electricforce equation needs the potential field calculated by the Electrostatic equation.
    4. Change the equation's solver settings or the general solver settings if necessary.

    The electricforce equation only calculates the force for faces with a FEM ConstraintElectrostaticPotential.svg electrostatic potential constraint if the constraint's option Calculate Electric Force is used.

    Solver Settings

    For the general solver settings, see the Elmer solver settings.

    The electricforce equation provides this special setting:

    • DataExec Solver: By default the equation is only solved after a timestep passed. This means it is first solved after the solution of other equations converged. When the setting is Always the equation is solved after every iteration within a time step. (For steady-state simulations the whole simulation is one time step.)

    Constraint Information

    The electricforce equation does not have own constraints. It takes the FEM ConstraintElectrostaticPotential.svg electrostatic potential constraint from the FEM EquationElectrostatic.svg Electrostatic equation. In the constraint it is important to use the option Calculate Electric Force.


    The result is the electric force density in .