1. Magnets

2. Properties of Magnets
A magnet is any material that attracts iron and materials that contain iron.
Magnets attract or repel other magnets.
One part of a magnet will always point north when allowed to swing freely
Magnets will point towards the North Star or Polaris, also known as the leading star, or lodestar.

3. Magnetic Poles A magnetic pole is the end of a magnet
North pole: end that points North
South pole: opposite end
Magnetic poles that are unlike attract each other, alike poles repel.
Just like electric charges!
Magnetic force is the attraction or repulsion between magnetic poles.
Produced when magnetic poles interact
Any material that exerts magnetic force is considered a magnet

4. Magnetic Fields
The magnetic field is the area of magnetic force around a magnet
Allows magnets to interact without touching
Magnetic field lines are the invisible lines that map out the magnetic field of a magnet
Form complete loops, never cross
Always leave north and enter south
Distance between field lines indicate the strength of the magnet
Closer the lines, stronger the lines

5. Magnetic Domains
A magnetic domain is a region where the magnetic fields of all atoms are lined up in one direction
If the material is NOT magnetized, the magnetic domain points in random directions
If the material is considered a magnet, the magnetic domains are arranged in the same direction

6. Magnetic Materials
A ferromagnetic material is a material that shows strong magnetic properties
Behaves like a piece of iron
Iron, nickel, cobalt, samarium
Alloy magnets - magnets made from several different metals
Alnico - aluminum, nickel, iron, cobalt
Platinum and cobalt
Ferrite - mixture of substances that contain ferromagnetic elements
Most commonly used today
Brittle material but inexpensive

7. Making Magnets Unmagnetized material can be magnetized
Placing an unmagnetized ferromagnetic material in a strong magnetic field
By rubbing the material with one pole of a magnet
Magnetizing a paper clip
Rub the paperclip in one direction along one pole of the magnet
Magnetic field of the magnet causes some domains in the paperclip to line up.

8. Destroying Magnets
Temporary magnet is a magnet made from a material that easily loses its magnetism
Permanent magnet is a magnet made from a material that keeps its magnetism for a long time
No magnet can last forever
Ways to demagnetize magnets
Drop it
Strike it
Heat it

9. Breaking Magnets
Break a magnet in half and you will have two smaller magnets
Each smaller magnet has its own north pole and south pole
Magnetic poles are lined up in one direction, which will remain even if the magnet is broken S N

10. Magnetic Earth

11. Earth as a Magnet
In the 1500s, Sir William Gilbert decided to investigate compasses
Gilbert confirmed that a compass always points in the same direction, no matter where you are
Gilbert hypothesized that the Earth is simply a giant magnet
Was Gilbert correct?

12. The Compass
The north pole of the magnet will point towards the North Pole
The poles of the magnetized needle on the compass align themselves with the Earth’s magnetic fields
The Earth does not actually have a bar magnet buried within its core – just an analogy!

13. The Unknown Core
Seismologists still do not completely understand Earth’s magnetism
They theorize that the inner core of the Earth is made up of molten iron
The circulation of molten material inside the Earth’s core is what causes Earth’s magnetism

14. Earth’s Poles
The Earth rotates on its axis around the geographic poles
The magnetic poles are located on Earth’s surface where the magnetic force is the strongest
Magnetic North Pole is actually located in Northern Canada – about 1,250 kilometers (about 776 miles) from the geographic North Pole
Magnetic declination is the angle between the two lines – geographic north and magnetic north

16. Earth’s Magnetic Field
Earth’s magnetic field acts on rocks
Rock is produced in the ocean floor from molten material that seeps up through the mid-ocean ridge
The iron in the rock lines up in the direction of the Earth’s magnetic field
Rock cools and hardens and the iron is locked in place
This process creates a permanent record of the magnetic field
As scientists have been studying such rocks, they have discovered that the direction and strength of the Earth’s magnetic field have changed over time
Earth’s magnetic field has completely reversed direction every million years or so

17. Mid-ocean ridge
Rock formed when Earth’s
Magnetic field was reversed
Rock formed when Earth’s
Magnetic field was normal
Oceanic crust
Earth’s mantle
Molten Material

18. The Magnetosphere
Van Allen belts – two regions that contain electrons and protons traveling at very high speeds

19. The Magnetosphere
Solar wind is a stream of electrically charged particles flowing at high speeds from the sun
Pushes against Earth’s magnetic field and surrounds the field
The region shaped by the field is known as the magnetosphere.

20. Pictures of
The Earth’s
Magnetosphere

21. Auroras
When high-speed, charged particles get close to Earth’s surface, they interact with atoms in the atmosphere
This results in the atoms giving off light
A curtain of shimmering bright light in the atmosphere
This glowing region caused by charged particles is called an aurora.
Known as The Northern Lights, or aurora borealis in the North and the Southern Lights or aurora australis in the South.