Electric Insulation
The Electric Insulation node, which is the default boundary condition, adds electric insulation as the boundary condition:
This boundary condition means that no electric current flows into the boundary. At interior boundaries, it means that no current can flow through the boundary and that the electric potential is discontinuous across the boundary. It is also applicable at symmetric boundaries where the potential is known to be symmetric with respect to the boundary.
Electric insulation as the default boundary condition is not applicable to interior boundaries. To add electric insulation to an interior boundary, add an Electric Insulation node in addition to the one that represents the default boundary condition.