Magnetism Section 1

Section 1: Magnets and Magnetic Fields

Preview• Key Ideas • Bellringer • Magnets • Magnetic Fields • Earth’s Magnetic Field

Magnetism Section 1

Magnets, continued

• Some materials can be made into permanent magnets.• A magnetized piece of iron is called a “permanent”

magnet, but its magnetism can be weakened or even removed.

• Iron is a soft magnetic material. • It is easily magnetized.• It tends to lose its magnetic properties easily.

• Cobalt is a hard magnetic material.• It more difficult to magnetize. • Once magnetized, it doesn’t lose its magnetism

easily.

Magnetism Section 1

Visual Concept: Magnetic Materials

Magnetism Section 1

Magnetic Fields〉What causes a magnet to attract or repel

another magnet?

〉Magnets repel or attract each other because of the interaction of their magnetic fields.

• magnetic field: a region where a magnetic force can be detected

Magnetism Section 1

Magnetic Fields, continued• Magnets are sources of magnetic fields.

• Moving charges create magnetic fields.• magnetic domains: groups of atoms that all line up

the same way and form small, magnetized regions within a material

• Magnetic field lines are used to represent a magnetic field.– Field lines always form closed loops.

• The magnetic field gets weaker with distance from the magnet.

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Magnetic Fields, continued

• Magnetic field lines that are close together indicate a strong magnetic field.

• Field lines that are farther apart indicate a weaker field.

• Magnetic field lines begin at the north pole of a magnet and end at the south pole of the magnet.

Magnetism Section 1

Magnetic Fields, continued

• Compasses align with Earth’s magnetic field.

– The compass points in the direction that lies along the magnetic field line at a given point.

– By convention, the pole of a magnet that points north is painted red.

Magnetism Section 1

Earth’s Magnetic Field

〉How is Earth’s magnetic field oriented?

〉Earth’s magnetic field lines run from geographic south to geographic north.

• The pole in Antarctica is a magnetic north pole.

• The pole in northern Canada is a magnetic south pole.

Magnetism Section 1

Earth’s Magnetic Field, continued

• Earth’s magnetic field has both direction and strength.• The source of Earth’s magnetism is not yet fully

understood.– The iron in the core is too hot to retain any

magnetic properties.– The circulation of ions or electrons in the liquid

layer of Earth’s core may be the source of the magnetism.

• The sun also has a magnetic field and ejects charged particles into space.