Iron filings attracted to a horseshoe magnet. Iron filings are sprinkled over a horseshoe magnet. The magnetic field between the poles of the magnet induces a magnetic field in each particle of iron, effectively turning each into a tiny bar magnet. These are attracted to the poles and can be levitated to follow the three-dimensional field. As the field weakens away from the poles, the field is no longer strong enough to levitate the filings against their own weight.