INTEGRATED SCIENCE 2014

Magnetism

History

Magnets name came from Magnesia (now a part of Greece)

First lodestones (naturally occurring magnetic rocks) were found there 3000 years ago.)

The ancient Greeks, Indians, and Chinese all have recorded writings that explore the properties of magnetism and its effects on other materials.

Magnets exert a magnetic field effect around them….this results from the chemical make-up of the materials that make up magnets.

Magnetic Poles

All magnets have a pair of poles (north & south)

Poles exert a force on each otherLike pole repel; unlike pole attractIf a magnet if cut in two, each piece will still

have two poles.

Permanent vs. Temporary Magnets

Some substance are magnetic all of the time (ex. lodestone, iron, nickel & cobalt) and have ferromagnetic magnetism.

Substances can also be made into magnets by contact or proximity

Temporary magnets can loose their magnetism by being hit or heated.

Hard vs. Soft Magnetism

Hard vs. soft magnetism: How materials retain their magnetic properties determines if they are “hard” or “soft”. Ex. Iron is soft since if heated or hit, it easily loses its magnetism.

Cobalt & nickel are difficult to magnetize, but don’t lose magnetism easily and so called hard magnetically.

Magnetic Field Lines

A magnetic field is a region where a magnetic force can be detected.

This is an attractive or repulsive force field.It surrounds any magnetized materialStrength determined by material of the

magnet, the distance from the magnet & how much it’s been magnetized.

Also can be created by moving charges.An atom is magnetic since the electrons

move!

Magnetic Domains

Like electric field lines, magnetic field lines can illustrate magnetic fields.

Always form closed loops.Greater distance in magnetic field from the

magnet, then weaker magnetic field.Closer lines together….then strong field….Magnetic field is strongest at the poles.

Compass

A compass shows the direction of the magnetic field

When a magnet is suspended to hang freely it will pivot.

Remember … opposites attract, so the north pole is pointing toward earth’s magnetic south pole. (explain this more on the next slide!)

On a traditional compass, that north seeking pole is painted red.

Earth’s Magnetic vs. Geographic Poles

They are not in the same place….The pole in Antarctica is actually a magnetic

north pole & geographic south pole.Earth’s geographic north pole is earth’s

magnetic south pole.Earth’s magnetic field lines run from North

magnetic pole to South magnetic pole.

Video 9m15s http://www.bing.com/videos/results.aspx?q=earths+magnetic+vs.+geopraphic+poles&form=MSNH14&refig=f653fa0fafcc47af908c765ad849466d&pq=earths+magnetic+vs.+geopraphic+poles&sc=0-18&sp=-1&qs=n&sk=#view=detail&mid=1B25CE2A0D758AE622291B25CE2A0D758AE62229