The Electrostatics (es) interface (), found under the AC/DC > Electric Fields and Currents branch when adding a physics interface, is used to compute the electric field, electric displacement field, and potential distributions in dielectrics under conditions where the electric charge distribution is explicitly prescribed. The formulation is stationary except for when it is used together with other physics interfaces. Eigenfrequency, frequency-domain, small-signal analysis, and time-domain modeling are supported in all space dimensions.

In addition to this standard formulation, the Electrostatics interface also has the option of using both the displacement field and the scalar potential as the dependent variables, see The D-V Formulation. This is set in the discretization settings for the electrostatics interface. The following sections in the Electrostatics interface chapter refer to the interface using the default V-formulation implementation. The information specific to the D-V formulation is given in the section The Electrostatics Interface Using the D-V Formulation.

When this physics interface is added, these default nodes are also added to the Model Builder — Free Space, Zero Charge (the default boundary condition), and Initial Values. Then, from the Physics toolbar, add other nodes that implement, for example, boundary conditions and space charges. You can also right-click Electrostatics to select physics features from the context menu.

The physics-controlled mesh is controlled from the Mesh node’s Settings window (if the Sequence type is Physics-controlled mesh). There, in the table in the Physics-Controlled Mesh section, find the physics interface in the Contributor column and select or clear the checkbox in the Use column on the same table row for enabling (the default) or disabling contributions from the physics interface to the physics-controlled mesh.

The Label is the default physics interface name.

The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first physics interface in the model) is es.

For 1D components, enter a default value for the Cross-section area A (SI unit: m2). The default value of 1 is typically not representative for a thin domain. Instead it describes a unit thickness that makes the 1D equation identical to the equation used for 3D components. See also Change Cross Section.

For 2D components, enter a default value for the Out-of-plane thickness d (SI unit: m). The default value of 1 is typically not representative for a thin dielectric medium, for example. Instead it describes a unit thickness that makes the 2D equation identical to the equation used for 3D components. See also Change Thickness (Out-of-Plane).

Enter a Reference impedance Zref (SI unit: Ω). The default is 50 Ω.

Select the Use manual terminal sweep checkbox to switch on the sweep and invoke a parametric sweep over the terminals. Enter a Sweep parameter name to assign a specific name to the variable that controls the terminal number solved for during the sweep. The Sweep parameter name must also be declared as a model parameter. The default is PortName.

The lumped parameters are subject to Touchstone file export. Enter a file path or Browse for a file. Select a Parameter format (value pairs) for the Touchstone export — Magnitude and angle (MA) (the default), Magnitude in dB and angle (DB), or Real and imaginary parts (RI). Select an option from the If file exists list — Overwrite or Create new. Create new is useful when the model is solved multiple times with different settings. Select a Parameter to export: Z (the default), Y, or S.

From the Home toolbar add a Parameters node and enter the chosen name and assign to it a temporary Expression of unity into the Parameters table. You can also right-click Global Definitions to add the node.

The dependent variable is the Electric potential V. You can change its name, which changes both the field name and the variable name. If the new name coincides with the name of another dependent variable in the model, the physics interfaces shares degrees of freedom. The new name must not coincide with the name of a field of another type or with a component name belonging to some other field.

In addition to the standard V formulation, the interface also has the option to use the D-V formulation, which is mixed formulation method based on using both the electric displacement field D and the electric potential V as dependent variables. This option is set in the discretization setting of the Electrostatics interface.

Select the shape order for the Electric potential dependent variable — Linear, Quadratic (the default), Cubic, Quartic, or Quintic. For more information about the Discretization section, see Settings for the Discretization Sections in the COMSOL Multiphysics Reference Manual.

The Mixed finite element options set the Electrostatics interface to use the D-V formulation. This uses divergence elements to compute the displacement field which can be set to use either type 1 (not labeled) or type 2. Both of these types of divergence elements are available in linear and quadratic orders. For more information on the divergence elements, see Shape Function Types (Element Types).