FEM EquationElectricforce

Description
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.

Usage

 * 1) After adding an Elmer solver as described here, select it in the tree view.
 * 2) Either use the toolbar button [[Image:FEM_EquationElectricforce.svg|32px]] or the menu.
 * 3) Now either use the toolbar button [[Image:FEM_EquationElectrostatic.svg|24px]] or the menu . 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 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:
 * : 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 electrostatic potential constraint from the  Electrostatic equation. In the constraint it is important to use the option Calculate Electric Force.

Result
The result is the electric force density in $$\rm N/m^2$$.