Line Charge
For 3D components, use the Line Charge node to specify line charges along the edges of a geometry. Add a contribution as a Harmonic Perturbation by right-clicking the parent node or clicking Harmonic Perturbation on the Physics toolbar. For more information see Harmonic Perturbation — Exclusive and Contributing Nodes in the COMSOL Multiphysics Reference Manual.
Edge Selection
Beware that constraining the potential on edges usually yields a current outflow that is mesh dependent.
Line Charge
Enter a value or expression to apply a Line charge QL (SI unit: C/m). This source represents electric charge per unit length and the default is 0 C/m.
Line Charge (on Axis) and Line Charge (Out-of-Plane)