Dipole Magnet and Iron Filings: visualizing the invisible- the magnetic field lines around a dipole magnet. In the presence of a magnetic field, ferromagnetic materials (such as iron) temporarily become magnets. In this device tiny iron filings each become dipole magnets and link end to end to follow and reveal the magnetic field lines associated with the permanent magnet within the center hollow tube. A simple yet functional magnetic field mapping device that reveals the presence and shape of t