Magnetism. Iron filings being attracted to a horseshoe-shaped magnet. The magnetic field of the magnet induces a small magnetic field in the iron filings, and the opposite magnetic poles than attract each other. As a horseshoe magnet has both a north (centre left) and south (centre right) pole, the iron filings are magnetically arranged in opposite directions. The iron filings will remain magnetised for a time after the bar magnet has been removed.