Magnetism
The Nature of Magnets
►Magnetism: force of attraction or repulsion Attraction to any substance that is, or can
become, a magnet►Rule of magnets:
Opposite poles attract Like poles repel
►Magnetic fields: area surrounding the magnet that influences other objects
►Poles: region of magnet where effects of magnet are strongest
A single magnet
Two magnets
►Magnetic domains: groups of atoms lined up together unmagnetized: groups are in random
patterns magnetized: atoms all (or mostly) line up
in one direction►Magnets made of iron, cobalt, nickel
Called ferromagnetic (“ferro-” for Fe or iron-like)
Atoms can rearrange to line up in these materials
What causes magnetism?
Domains
The Earth as a magnet
►Demonstration of magnet and “lodestone”
►compass always points to North►Why?►The earth itself is a magnet
strongest force is at the poles of the magnet (The North and South Pole!)
Inner core of molten iron and nickel spinning
►Poles switch about every 500,000 years evidence in rock
samples
The Sun’s Effect on Earth
►Solar wind: charged particles from the sun would destroy us if earth had no magnetic field
►Cause interference for TV, Cell phones
►Auroras: Northern and Southern Lights charged particles hit a
tmosphere at the Poles and cause the air to glow Video of AurorasAuroras in Finland
►Brainpop on magnetism►DVD on magnetism
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