=== Gaps Sources on PEC Wires and Strips ===
A Gap is an infinitesimally narrow discontinuity that is placed on the path of the current. In EM.Libera, a gap is used to define an excitation source in the form of an ideal voltage source. Gap sources can be placed on PEC '''Thin Wire Line''' and '''Polyline''' objects to provide excitation for the Wire MoM solver. The gap splits the wire into two lines with a an infinitesimally small spacing between them, across which the ideal voltage source is connected.
{{Note|If you want to excite a curved wire antenna such as a circular loop or helix with a gap source, first you have to convert the curve object into a polyline using [[CubeCAD]]'s Polygonize Tool.}}