1. MAGNETISM

2. History of Magnetism Discovered by the Chinese
Used by magicians and sailors
Illusions…..
Magnetic Hill, New Brunswick
Bermuda Triangle

3. Categories of Substances
Three Categories
Magnetic
Ferromagnetic
Non-magnetic

4. Magnetic
Attract or repel
Invisible fields
Object that has a field and that can attract some other objects.
Example: horseshoe magnet

5. Ferromagnetic Is attracted by a magnet Can be magnetized
Not a magnet
Is attracted by a magnet
Can be magnetized
Must contain iron,
nickel or cobalt
eg: paper clip or nail

6. Non-Magnetic Is not attracted by a magnet
Example: glass, plastic, or wood

7. Important Facts about Magnets
All magnets have two poles, a North (N) and a South (S). They are known as dipoles.
Fields are infinite in size & 3-Dimensional
Similar poles repel & opposite poles attract.
Repulsion
Attraction

8. Poles N attracts South S attracts North N repels North S repels South
Opposites
attract
Likes
repel

9. Mapping Magnetic Fields
Remember
the lines never cross
Always goes from North to South
Closer the lines, stronger the attraction
Around a magnet there are lines of force that have direction and strength (magnetic field). S N

10. Compass S N S N S The needle of the compass is magnetic
North
end
The needle of the compass is magnetic
Red Tip of needle is North
Red Tip will always be attracted towards South S
Tip of arrow
Is North therefore
It is attracted to South N S
Example #1 N S
Example #2

11. Why the Compass Works
Geographic North
Geographic South

12. Why the Compass Works
Magnetic South N S
Magnetic North

13. Key Points to Remember
Magnetism is a property that makes certain material attract or repel.
Ferromagnetic
Attracted by magnet
Must contain Fe, Ni, Co
Nonmagnetic
Not attracted by magnet
Opposites attract (i.e N & S)
Likes Repel (i.e. S & S or N & N)
Magnetic Field
Arrows always go from north to south (outside magnet)
Lines of force never cross
The closer the lines, the stronger the field
Compass
Red portion of compass needle is North and is always attracted to South
HINT
Nerd to
Sexy

14. Origins of Magnetism of Matter
Scientists believe that magnetism comes from spinning electrons around the nucleus of the atom.
When atoms clump together they form a domain.

15. Origins of Magnetism of Matter
Similar electron spins produce a strong domain, where as opposite electron spins cancel one another out and produce a weak domain.
If enough domains align in the same direction, this will create a magnetic field.

16. How to Magnetize an Object
Bring the ferromagnetic substance in contact with another magnet.
Bang the ferromagnetic substance (example: striking a nail repeatedly).
Heat up the substance and cause the domains to align.
Run electric current through the ferromagnetic substance.
Please note that all of these methods can also de-magnetize a magnet.