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Magnets

Magnets. Certain minerals were known to attract iron objects. Magnetite or lodestone Property called magnetism Iron could attract other iron as well. Iron could be treated with lodestone to gain the same magnetism. Permanent magnet. Lodestone. Magnetized objects can attract or repel.

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Magnets

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  1. Magnets

  2. Certain minerals were known to attract iron objects. Magnetite or lodestone Property called magnetism Iron could attract other iron as well. Iron could be treated with lodestone to gain the same magnetism. Permanent magnet Lodestone

  3. Magnetized objects can attract or repel. Depends on the end of the magnet The ends are called poles. Labeled north and south Force direction depends on the poles. North attracts south North repels north South repels south Poles

  4. A bar magnet with two poles is a dipole. If the magnet is split each part becomes a new dipole. The splitting can continue to the microscopic level. Magnetic objects can have more than two poles. Never one pole Dipole One bar magnet N S N S N S Split into two

  5. Lined Up • Field lines connect magnetic poles. • Similar to electric fields by charges

  6. Magnetic Field • The magnetic field (B) indicates the strength and direction of the magnetic force. • The unit of magnetic field is the tesla (T). • 1 T = 1 N/A m • The gauss is an alternate unit for magnetic field. • 1 gauss = 10-4 T

  7. Different materials respond differently to magnetism. Ferromagnetic materials experience a noticeable force. Iron, nickel, cobalt Used in making magnets and magnetic media Diamagnetic materials are very slightly repelled by magnetism. Water, glass, plastics, gases Present in all substances due to atomic electrons Paramagnetic materials are very slightly attracted by magnetism. Aluminum, platinum Due to extra electrons forming atomic scale magnets Magnetic Material

  8. Magnetic fields are created by moving charges. Atomic electrons move in magnetic materials. Currents move in wires. Some typical magnetic fields Human body – 3 x 10-10 T Radio wave – 1 x 10-9 T Computer monitor – 1 x 10-6 T Sunlight – 3 x 10-6 T Blender – 1 x 10-5 T Transmission line – 5 x 10-5 T Earth – 5 x 10-5 T Hair dryer – 3 x 10-4 T Small bar magnet – 1 x 10-2 T Lab electromagnet – 5 T Environmental Magnetism

  9. The iron core of the earth generates a magnetic field. North Pole is near a south magnetic pole. Does not match pole Flips on geological time scales Earth’s Field next

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