English: A diagram of the magnetic field (green) of a typical electromagnet, showing the field lines. The drawing shows a section through the core of the electromagnet except for the windings (red), which are shown in three dimensions for clarity. The iron core of the electromagnet (C) forms a closed loop for the magnetic flux, with two air gaps (G) in it. Most of the magnetic field (B) is confined to the core circuit. However some of the magnetic field lines (B_L) take "short cuts" and do not pass through the entire core circuit and so do not contribute to the force exerted by the magnet; this is called "leakage flux". This also includes magnetic field lines that encircle the wire windings without entering the core. In the gaps (G}, the magnetic field lines are no longer confined by the core, so they "bulge" out of the edges of the gap before bending back to enter the next piece of core material. These bulges (B_F) are called "fringing fields" and reduce the strength of the magnetic field in the gaps. The blue line L is the average length of the flux path or magnetic circuit, and is used to calculate the magnetic field.

This is a freehand drawing and is not quantitatively accurate as are images of magnetic field lines produced by computer.