Domain, Boundary, Edge, Point, and Pair Nodes for the Electrostatics Interface
The Electrostatics interface has these domain, boundary, edge, point, and pair nodes available.
About the Boundary Conditions
The relevant physics interface condition at interfaces between different media is
In the absence of surface charges, this condition is fulfilled by the natural boundary condition
Available Nodes
These nodes, listed in alphabetical order, are available from the Physics ribbon toolbar (Windows users), Physics context menu (Mac or Linux users), or right-click to access the context menu (all users). Also see Table 10-2 for a list of interior and exterior boundary conditions, including edge, point, and pair availability.
In general, to add a node, go to the Physics toolbar no matter what operating system you are using. Subnodes are available by clicking the parent node and selecting it from the Attributes menu.
•
Change Cross Section
•
Change Thickness (Out-of-Plane)
•
Charge Conservation
•
Charge Conservation, Piezoelectric1
•
Electric Displacement Field
•
Electric Potential
•
External Surface Charge Accumulation
•
Ground
•
Initial Values
•
Line Charge
•
Line Charge (on Axis)
•
Line Charge (Out-of-Plane)
•
Periodic Condition
•
Point Charge
•
Point Charge (on Axis)
•
Space Charge Density
•
Surface Charge Density
•
Thin Low Permittivity Gap
•
Zero Charge (the default boundary condition)
1 This feature is available with the Piezoelectricity interface, which requires the Acoustics Module, MEMS Module, or the Structural Mechanics Module.
Table 10-2 lists the interior and exterior boundary conditions available with this physics interface. It also includes edge, point, and pair availability.
Table 10-2: Interior and Exterior Boundary Conditions (including Edge, Point, and Pair Availability) for the Electrostatics Interface
Node
Interior
Exterior
Also Available For
Change Cross Section
x
x
pairs
Change Thickness (Out-of-Plane)
x
x
pairs
Electric Displacement Field
x
x
pairs
Electric Potential
x
x
edges, points, and pairs
External Surface Charge Accumulation
 
x
pairs
Ground
x
x
edges, points, and pairs
Periodic Condition
 
x
not applicable
Surface Charge Density
x
x
pairs
Thin Low Permittivity Gap
x
 
not applicable
Zero Charge (the default)
x
x
pairs
For axisymmetric components, COMSOL Multiphysics takes the axial symmetry boundaries (at r = 0) into account and automatically adds an Axial Symmetry node to the model that is valid on the axial symmetry boundaries only. There are also Line Charge (on Axis) and Point Charge (on Axis) available.
In the COMSOL Multiphysics Reference Manual, see Table 2-4 for links to common sections and Table 2-5 to common feature nodes. You can also search for information: press F1 to open the Help window or Ctrl+F1 to open the Documentation window.