Magnetism

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Slide 1

Magnetism

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Magnets have been known for centuries.

The Chinese and Greeks knew about the “magical” properties of magnets. The ancient Greeks used a stone substance called “magnetite.” They discovered that the stone always pointed in the same direction. Later, stones of magnetite called “lodestones” were used in navigation.

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William Gilbert, an English physician, first proposed in 1600 that the earth itself is a magnet, and he predicted that the Earth would be found to have magnetic poles.

Slide 4

What is Magnetism?

Magnetism is the force of attraction or repulsion of a magnetic material due to the arrangement of its atoms, particularly its electrons.

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All magnetic phenomena result from forces between electric charges in motion.

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The ends of a magnet are where the magnetic effect is the

strongest. These are called “poles.” Each magnet has

2 poles – 1 north, 1 south.

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Like repels like…

Opposites attract!

Slide 8

Poles of a magnet always

Come in pairs!

Slide 9

If you cut a magnet in half,

you get 2 magnets!

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N

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N

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N

Slide 10

No Monopoles Allowed

It has not been shown to be possible to end up with a single North pole or a single South pole, which is a monopole ("mono" means one or single, thus one pole).

Note: Some theorists believe that magnetic monopoles may have been made in the early Universe. So far, none have been detected.

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Slide 11

Magnetic Fields

The region where the magnetic forces

act is called the “magnetic field”

Slide 12

Defining Magnetic Field Direction

Magnetic Field vectors as written as B

Direction of magnetic field at any point is defined as the direction of motion of a charged particle on which the magnetic field would not exert a force.