Magnetism Magnetic Force 1 Definition of Magnetic Field Cross Products Bar Magnets Horseshoe Magnets The Earth’s Magnetic Field.

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Definition of Magnetic Field

Cross Products

Bar Magnets

Horseshoe Magnets

The Earth’s Magnetic Field

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Definition of Magnetic Field

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Properties of a magnetic field

Definition of a Magnetic Field

A magnetic field is a set of vectors found everywhere in space. These vectors describe the interaction between moving charges and other moving charges.

What magnetic fields are not …

1. They are not themselves charges.2. They are not electric (or any other) fields.3. They are not contained in charges.4. They are not forces.

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Magnetic fields are caused by the movement of charge.

Magnetic fields also put forces on moving charges.

Magnetic fields are in addition to electric fields.

Magnetism is NOT the same as electricity.

Magnetic objects have North and South poles.

For every North pole there is an attached South pole.You can’t have one without the other.

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Cross Products

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1. Point the fingers of your right hand in the direction of the vector A.

2. Curl your fingers toward the direction of the vector B.

3. The cross-product vector C is given by the direction of your thumb.

A

B C

This movie is availabale as a separate file.

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Bar Magnets

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N SN S

NN

Bar Magnets get their magnetism from spinning electrons. The spin axis of these electrons align. This is called Ferromagnetism

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N SN S

The direction of the magnetic field vector at any point in space is easily found by using a smaller magnet. This smaller magnet we call a compass.

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N SN S

If we draw the field lines that correspond to these field vectors, they would look like this.

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Horseshoe Magnets

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N SN S

If we draw the field lines of a bar magnet, they look like this.

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The Earth’s Magnetic Field

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The magnetic field of the earth is stretched by the solar wind.