Magnetic fringing
= Magnetic fringing
<Magnetic fringing> is the spreading of <magnetic field lines> near an air gap or pole edge, so the gap's effective <magnetic flux> area exceeds its geometrical pole-face <area>. A gap much shorter than its transverse dimensions permits a leading uniform-field approximation. High core <magnetic permeability> does not by itself justify neglecting <magnetic fringing> for a wide gap.