Magnetism is one of the main forces of nature. Like the force of gravity, which causes objects to be attracted to each other, magnetism causes magnetized objects to be attracted to each other. Simple dipole magnets have two poles: a "North" pole and a "South" pole. If two magnetic objects are brought together, the North pole of one will “stick” to the South pole of the other.
In this activity, the magnetic chips or filings align themselves along the lines of magnetic force. These lines of force point from the positive pole to the negative pole of the magnet. When students sprinkle magnetic chips onto their magnet they first learn that the chips are magnetic (because they “stick” to the magnet). They then explore how magnetism forces the chips to line up in the direction the magnetic force points, allowing them to see the shape of the magnetic field.
Earth is an example of a dipole magnet, where the lines of force point in a direction out of the South (magnetic) Pole and into the North (magnetic) Pole. The magnetic field is made by currents of molten material which move around deep within our planet. On Earth, a simple compass can always be used to detect the presence of the magnetic field of the Earth, as well as any other nearby magnetic fields such as magnetic metals (refrigerator doors, for example). The needle of the compass acts like the magnetic chips or filings used in this activity.
This activity was developed by staff at the UCAR Center for Science Education.