Download Lodestone - naturally occuring mineral of iron with magnetic

Lodestone - naturally occuring mineral of iron with magnetic
properties
Magnetism - along with electricity, forms one of the
fundamental forces
- caused by the movement of electrons
- revolution of the electrons around the nucleus
- intrinsic property of electrons called "spin"
- used to believe the electrons spun on their axis
"It was first hypothesized that this... ...was due to angular
momentum associated with a spinning of the electron. That is,
the electron might spin on its axis as well as orbit the nucleus,
just as the earth spins on its axis and orbits the sun. ...Today
we consider this picture... ... as not legitimate. What is
important is that the electron can have two different states
due to some intrinsic property that behaves like angular
momentum, and we call this property "spin."
Ferromagnetic - substances that are strongly attracted to
magnets
- iron, cobalt and nickel (and gadolinium)
- caused by "spin" of several unpaired electrons
Diamagnetic - substances that are weakly repelled by magnets
- caused by revolution of electrons around nucleus
Paramagnetic- substances that are weakly attracted to magnets
- caused by the effect of spin being slightly greater than
revolution around nucleus
Domains ­ microscopic regions in ferromagnetic materials in which dipoles align in same direction
­ ferromagnetic materials become magnets when the alignment
of the domains is in the same direction
­ when magnet is brought nearby, domains shift to align with magnet, this is called "induced magnetism"
­ sometimes the magnetism is retained and is called "residual
magnetism"
­ to permanently "magnetize" a ferromagnetic material, the domains must all be aligned
Domains Before Magnetization
Domains After Magnetization
It is believed that the earth's magnetic field is produced by the movement of molten iron in the outer core.
The earth has magnetic poles located near the geographic poles. The "N" pole of a bar magnet or compass is attracted to our geographic north pole. Therefore it is a magnetic south pole. Magnetic declination ­ the angle in degrees from magnetic N to geographic "north", 0­5 degrees east in Minnesota
North Geographic Pole
South Magnetic Pole
South Geographic Pole
North Magnetic Pole
In 1820, Oersted discovered that a wire carrying current can deflect a compass. If the current is reversed, so does the compass. The field lines circle the wire in a perpendicular fashion, as seen in the following animation.
Magnetic Field Around a Current­Carrying Wire
Ampere's Right­Hand Rule ­ if the thumb points in the direction of the positive current flow (not electrons), the fingers wrap around the wire in the direction of the magnetic field (same direction that "N" on a compass would).