1. Table of Contents
What Is Magnetism?
Inside a Magnet
Magnetic Earth

2. - What Is Magnetism?
Properties of Magnets
A magnet is any material that attracts iron and materials that contain iron
A mineral with magnetic properties was first discovered in ancient Greece 2,000 years ago and was named “magnetite” after the city Magnesia.
If left to swing freely, a magnet will always point north, where the north star (Polaris) is located.

3. - What Is Magnetism?
Magnetic Poles
Magnetic pole – the ends of a magnetic object, where the magnetic force is strongest.
A magnet always has a pair of poles, a north pole and a south pole.
Magnetic poles that are unlike (opposite) attract each other, and magnetic poles that are alike repel each other.

4. - What Is Magnetism?
Magnetic Force
Magnetic Force - the attraction or repulsion between magnetic poles.
Can create a push or a pull that can cause an object to move
Magnetic forces occur naturally, but can be used by man.
Ex. Toy trains

5. - What Is Magnetism?
Magnetic field
Magnetic field – the region around a magnet where the magnetic force is exerted.
Is strongest at the poles of a magnet, but it surrounds the magnet
Can cause magnets to interact without even touching
Magnetic field lines – invisible lines that map out the magnetic field around a magnet

6. - What Is Magnetism?
Magnetic Fields
Magnetic field lines spread out from one pole, curve around the magnet, and return to the other pole.

7. - What Is Magnetism?
Magnetic Fields
When the magnetic fields of two or more magnets overlap, the result is a combined field.

8. A Single Magnetic Field
- What Is Magnetism?
A Single Magnetic Field
Although you cannot see a magnetic field, you can see its effects.
The photograph shows iron filings sprinkled on a sheet of plastic that covers one magnet.

9. Combined Magnetic Fields
- What Is Magnetism?
Combined Magnetic Fields
This picture shows the magnetic field produced when the poles of two bar magnets are brought near each other.
Compare the combined field of two like poles to that of two unlike poles.

10. Magnetic Field Lines Activity
- What Is Magnetism?
Magnetic Field Lines Activity
Click the Active Art button to open a browser window and access Active Art about magnetic field lines.

11. - Inside a Magnet
The Atom
The magnetic properties of a material depend on the structure of its atoms.
Atom – smallest particle of an element that has the properties of that element.
Element – one of about 100 basic materials that make up all matter.

12. The Atom Atoms consist of:
- Inside a Magnet
The Atom
Atoms consist of:
Nucleus - center region of an atom that contains protons and neutrons
Proton – a particle that carries a positive charge
Neutron – a particle that does not carry a charge.

13. The Atom Electron – particle that carries a negative charge.
- Inside a Magnet
The Atom
Electron – particle that carries a negative charge.
move randomly throughout the atom
much smaller than neutrons and protons

14. - Inside a Magnet
Electron Spin
A spinning electron produces a magnetic field that makes the electron behave like a tiny magnet in an atom.
Electrons form pairs that spin in opposite directions
If an atom looses or gains an electron it will increase the atoms magnetic field.

15. - Inside a Magnet
Magnetic Domains
Magnetic domain – region in which the magnetic fields of all atoms are lined up in the same direction.
If this occurs it creates a magnetic property in an object
If the fields are not aligned (pointing in the same direction) then the object does not have a magnetic property.

16. - Inside a Magnet
Magnetic Domains
In a magnetized material, all or most of the magnet domains are arranged in the same direction.

17. - Inside a Magnet
Magnetic Materials
Ferromagnetic material – a material that shows strong magnetic properties
In nature, iron, nickel, cobalt, and gadolinium are common ferromagnetic materials
The magnets that we use are usually made from alloys.
Alloy – a combination of several metals
Ex. alnico – alloy made of aluminum, nickel, iron, and cobalt

18. - Inside a Magnet
Magnetic Materials
Modern magnets come in a variety of shapes and are made from many different materials.

19. Making and Changing Magnets
- Inside a Magnet
Making and Changing Magnets
No magnet can last forever. Magnets can be made, destroyed, or broken apart.
Magnets can be made by…
placing an unmagnetized ferromagnetic material in a strong magnetic field
rubbing the material with one pole of a magnet.
Temporary magnet - made from a material that easily loses its magnetism

20. Making and Changing Magnets
- Inside a Magnet
Making and Changing Magnets
Permanent magnet – made of material that keeps its magnetism.
Harder to magnetize
Permanent magnets can also be destroyed by…
Dropping or striking the magnet
Heating the magnet
Magnets can also be broken in two.

21. Making and Changing Magnets
- Inside a Magnet
Making and Changing Magnets
When a magnet is broken, each piece of a magnet retains its magnetic properties after it is cut in half.

22. Links on Magnetic Materials
- Inside a Magnet
Links on Magnetic Materials
Click the SciLinks button for links on magnetic materials.

23. - Magnetic Earth
Earth as a Magnet
Turn to pages in your textbooks. Read the first two paragraphs on pages 22 and 23 before beginning section 3 “Magnetic Earth”

24. - Magnetic Earth
Earth as a Magnet
Just like a bar magnet, Earth has a magnetic field surrounding it and two magnetic poles.

25. - Magnetic Earth
Earth as a Magnet
The magnetic poles are located on Earth’s surface where the magnetic force is strongest.
They are located close to the axis poles but not exactly at them (about 1,250 km off)
Because of this, a compass will not point directly to the north (axis) pole.
Magnetic declination – angle between geographic north and the north to which a compass needle points.

26. - Magnetic Earth
Earth as a Magnet
The location of Earth’s magnetic poles does not stay the same.
Therefore, the magnetic declination changes over time.

27. Movement of Earth’s Magnetic Poles
- Magnetic Earth
Movement of Earth’s Magnetic Poles
Earth’s magnetic poles move slowly over time. The data in the table show the position of Earth’s magnetic north pole in specific years.

28. Movement of Earth’s Magnetic Poles
- Magnetic Earth
Movement of Earth’s Magnetic Poles
Interpreting Data:
What is the trend in the speed of the pole’s movement?
The average speed of the pole’s movement is increasing.

29. Movement of Earth’s Magnetic Poles
- Magnetic Earth
Movement of Earth’s Magnetic Poles
Calculating:
What is the total distance the pole has traveled over the time shown?
Between 1948 and 2001, the pole has moved 857 km (150 km km +120 km km km).

30. Movement of Earth’s Magnetic Poles
- Magnetic Earth
Movement of Earth’s Magnetic Poles
Predicting:
Using the data, predict the average speed of the pole’s movement between 2001 and Explain.

31. Movement of Earth’s Magnetic Poles
- Magnetic Earth
Movement of Earth’s Magnetic Poles
The average speed increased by 23 km/yr from 1994 to That is an increase of 3.3 km/yr per year. There are 9 years between 2001 and Therefore, a good prediction is that the average speed in 2010 will be 29.7 km/yr.

32. Earth’s Magnetic Field
- Magnetic Earth
Earth’s Magnetic Field
Since Earth produces a strong magnetic field, Earth itself can make magnets out of ferromagnetic materials.
Can attract domains strong enough to line them up in the same direction.
Ex. If you left a metal bar lying in a North-South direction for many years, the Earth could magnetize the bar.
The same thing may happen to newly formed rocks on the ocean floor.

33. Earth’s Magnetic Field
- Magnetic Earth
Earth’s Magnetic Field
When molten material hardens into the rock of the ocean floor, the direction of the Earth’s magnetic field at that time is permanently recorded.

34. The Magnetosphere
Earth’s magnetic field affects the movements of electrically charged particles in space and visa versa.
Van Allen belts – two doughnut-shaped regions 1,000–25,000 kilometers above Earth that contain electrons and protons traveling at high speed.

35. The Magnetosphere
Solar winds – streams of electrically charged particles flowing at high speeds from the sun
Magnetosphere – region of Earth’s magnetic field shaped by the solar wind.

36. - Magnetic Earth
The Magnetosphere
The solar wind causes Earth’s magnetic field to stretch out on the side of Earth not facing the sun.

37. The Magnetosphere Recall from the space chapters….
Aurora – glowing region produced by the interaction of charged particles from the sun and atoms in the atmosphere.
In the Northern Hemisphere, an aurora is called the Northern Lights, or aurora borealis.
In the Southern Hemisphere, it is called the Southern Lights, or aurora australis.

38. Click the Video button to watch a movie about auroras.
- Magnetic Earth
Auroras
Click the Video button to watch a movie about auroras.

39. More on Earth’s Magnetic Field
- Magnetic Earth
More on Earth’s Magnetic Field
Click the PHSchool.com button for an activity about Earth’s magnetic field.

40. Graphic Organizer Magnets Magnetic fields Magnetic domains
produce
have atoms grouped in
Magnetic fields
strongest at
mapped by
Magnetic domains
Magnetic field lines
The poles