Magnets

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

Poles  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

Dipole  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 NS NSNS One bar magnet Split into two

Lined Up  Field lines connect magnetic poles. Similar to electric fields by chargesSimilar to electric fields by charges

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 m1 T = 1 N/A m  The gauss is an alternate unit for magnetic field. 1 gauss = T1 gauss = T

Magnetic Material  Different materials respond differently to magnetism.  Ferromagnetic materials experience a noticeable force. Iron, nickel, cobaltIron, nickel, cobalt Used in making magnets and magnetic mediaUsed 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

Environmental Magnetism  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 T Radio wave – 1 x T Computer monitor – 1 x T Sunlight – 3 x T Blender – 1 x T Transmission line – 5 x T Earth – 5 x T Hair dryer – 3 x T Small bar magnet – 1 x T Lab electromagnet – 5 T

Earth’s Field next  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