Introduction to Introduction to MagnetismMagnetism

Warm-upWarm-up

Why does the magnet stick to the Why does the magnet stick to the whiteboard?whiteboard?

History of MagnetismHistory of Magnetism

The term The term magnetismmagnetism stems from a rocks stems from a rocks found in the region of Magnesia, Greece found in the region of Magnesia, Greece called called lodestoneslodestones..

In the 1100’s, the Chinese used magnets In the 1100’s, the Chinese used magnets to help navigate their ships and created to help navigate their ships and created the first compasses.the first compasses.

In the 1700’s Charles Coulomb studied the In the 1700’s Charles Coulomb studied the forces between lodestones.forces between lodestones.

Hans Christian OerstedHans Christian Oersted

In 1819, Danish scientist discovered the In 1819, Danish scientist discovered the relationship between electric currents and relationship between electric currents and magnetism.magnetism.

This lead to a world-wide search for the This lead to a world-wide search for the links between electricity and magnetism.links between electricity and magnetism.

We will be discussing all of these links We will be discussing all of these links later this weeklater this week

Magnetic PolesMagnetic Poles

Why do magnets repel if they are oriented Why do magnets repel if they are oriented one way, but attract if they are oriented one way, but attract if they are oriented another way?another way?

Magnetic PolesMagnetic Poles

Magnets have two poles, North and South.Magnets have two poles, North and South. The magnetic fields are strongest at the The magnetic fields are strongest at the

North and South poles, and weaker the North and South poles, and weaker the farther you get away from them.farther you get away from them.

What happens if you break a magnet? Is What happens if you break a magnet? Is it possible to isolate a pole?it possible to isolate a pole?

Using a compass, let us find which pole is Using a compass, let us find which pole is which on each magnet.which on each magnet.

What happens when we put a North Pole What happens when we put a North Pole near a South pole?near a South pole?

What happens when we put a South Pole What happens when we put a South Pole near a North Pole?near a North Pole?

How does a Compass Work?How does a Compass Work?

If a compass is held on a table, without If a compass is held on a table, without anything near it, how come the needle anything near it, how come the needle points in a specific direction?points in a specific direction?

Earth’s Magnetic PolesEarth’s Magnetic Poles

The Earth has a magnetic field, so The Earth has a magnetic field, so therefore, a compass with a needle that is therefore, a compass with a needle that is attracted to magnetic poles (like a paper attracted to magnetic poles (like a paper clip) points towards the poles.clip) points towards the poles.

Ready for the confusing part… the Ready for the confusing part… the geographic North Pole is actually the geographic North Pole is actually the magnetic magnetic South PoleSouth Pole… and it isn’t located … and it isn’t located directly Northdirectly North

The magnetic South pole, is located just The magnetic South pole, is located just North of the Hudson Bay in Canada.North of the Hudson Bay in Canada.

That is 1500km away from the Earth’s That is 1500km away from the Earth’s Geographic North Pole. Geographic North Pole.

earth's magnetic field

Why is the Earth Magnetic?Why is the Earth Magnetic?

Although the Earth has large deposits of Although the Earth has large deposits of iron ore beneath its surface (a magnetic iron ore beneath its surface (a magnetic substance), the high temperatures prevent substance), the high temperatures prevent the iron from retaining magnetism.the iron from retaining magnetism.

It is It is predictedpredicted that the magnetic field is due that the magnetic field is due to the movement of convection currents at to the movement of convection currents at the Earth’s core.the Earth’s core.

Are other planets magnetic?Are other planets magnetic?

There is evidence that the rate of rotation There is evidence that the rate of rotation is related to the strength of a planet’s is related to the strength of a planet’s magnetic field. magnetic field.

For example, Jupiter rotates faster than For example, Jupiter rotates faster than Earth and has a stronger magnetic field. Earth and has a stronger magnetic field.

How are some rocks magnetic and How are some rocks magnetic and some not?some not?

Iron ore achieves magnetism because it is Iron ore achieves magnetism because it is subjected to the Earth’s magnetic field subjected to the Earth’s magnetic field over long periods of time.over long periods of time.

Observe what happens to the paper clip Observe what happens to the paper clip as it is attached to a permanent magnet as it is attached to a permanent magnet for a long period of time. for a long period of time.

Magnetic Field linesMagnetic Field lines

Just like electric fields, magnetic fields can Just like electric fields, magnetic fields can be shown through field lines.be shown through field lines.

Predict what the field lines would look like Predict what the field lines would look like for the following magnet:for the following magnet: