- To show the shape of the magnetic field about a bar magnet and a horseshoe magnet.
The magnet is positioned on the overhead projector so that its image is projected on the screen. Projection tray is placed on top of the magnet. Place the "shallow" side of projecting tray facing down over the Bar magnet. Iron filings are sprinkled on to it. The pattern of the magnetic field is formed and is projected together with magnet's image.
Remove the "keeper" from the horseshoe magnet, and replace the bar magnet with the horseshoe magnet, and sprinkle iron filings on the tray. Observe the new magnetic field pattern.