The Gap Feed subnode is available from the context menu (right-click the
Single Conductor Coil parent node) or from the
Physics toolbar,
Attributes menu for 3D components (at the domain level).
Gap Feed is used to excite the coil from an interior boundary. It applies a discontinuity in the coil potential across a boundary to enforce a potential difference or a prescribed current. This feature must be applied to an interior boundary in the coil domain, and is typically used to excite a closed loop.