CORDELIA MOLLOY / SCIENCE PHOTO LIBRARY CORDELIA MOLLOY / SCIENCE PHOTO LIBRARY
Magnetic attraction. The iron filings sprinkled between these two bar magnets reveal the shape of the attractive magnetic field between them. The filings show the attraction as field lines joining the ends of the magnets. Bar magnets have a north and a south pole. Unlike poles attract each other, whereas like poles repel each other. The lines do not actually exist, as the magnetic field is continuous, but attractions between the filings make them arrange themselves into thin arcs.
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