Surface Current Density
The Surface Current Density boundary condition
specifies a surface current density at both exterior and interior boundaries, respectively. The current density is specified as a three-dimensional vector, but because it needs to flow along the boundary surface, COMSOL Multiphysics projects it onto the boundary surface and neglects its normal component. This makes it easier to specify the current density and avoids unexpected results when a current density with a component normal to the surface is given.
For Transition Boundary Condition, the Surface Current Density subnode as an one-sided surface current density is available from the context menu (right-click the Transition Boundary Condition parent node) or from the Physics toolbar, Attributes menu.
Surface Current density
Enter values or expressions for the components of the Surface current density Js0 (SI unit: A/m).
For the Surface Current Density subnode, select Side — Upside (the default) or Downside to define on which side the Surface Current Density is applied. The red arrow visualized on the selected boundaries always indicates the upside.