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