MAGNETISM

Magnetism Magnet – a material that has polarity – two opposite ends; the N-pole and the S-pole Example: the Earth- a giant magnet (south pole of the earth’s magnetic field is actually somewhere near true north) Think of how a compass points!

Magnetism Microscopic Picture of Magnets… The electrons moving within the individual atoms of the material create a tiny magnetic field When neighboring atom’s fields line up, they create DOMAINS- these are extremely small A magnet is formed when all of the domains in a material line up

Temporary Magnets Some metals can be polarized when brought close to naturally occurring magnets Ferromagnetic Materials – IRON, NICKEL, COBALT- the domains line up in the presence of the external magnetic field. They are temporary because the materials lose polarity when separated from the magnetic field.

Permanent Magnets Because of the microscopic structure of certain materials, polarization becomes permanent. ALNICO } iron alloy (Al 8%, Ni 14%, Co 3%) Most permanent magnets are made up of these materials Rare Earth elements: Neodymium, Gadolinium If you break a magnet into smaller pieces, the pieces will be smaller magnets. You cannot create a monopole.

Magnetic Fields Around Magnets Magnetic Field – field around a magnet in which a force is felt. Either attraction or repulsion This force is felt even at distances. Direction of the Field is determined by the direction that a N-pole of a compass points when placed in the field Fields can be visualized by the use of iron filings- each filing becomes a tiny magnet that lines up tangent to the field at a certain point.

Magnetic Fields Around Magnets

Strength of Magnetic Fields Magnetic Flux – the number of magnetic field lines passing through a surface Flux Density – the flux per unit area ~ proportional to the strength of the field Symbol: β ~ the flux is most concentrated at the poles the # of field lines = flux the # of field lines per unit area = FLUX DENSITY or MAGNETIC FIELD STRENGTH