1. Magnetism
ESCI 215
Chapter 6

2. Magnetite Magnetism was discovered more than 3000 years ago
Certain rocks (magnetite) attracted bits of iron
Magnetite formed from the slow hardening of the earth’s crust
The earth’s magnetic field made it magnetic
Magnetite was used by sailors in 1200 BC to point the way north
This allowed them to always know which way they were going regardless of weather, day/night, etc.

3. What Causes Magnetism? Substances are made up of atoms
Atoms can have a positive or negative charge
In non-magnetic substances (i.e. paper, wood, plastic), the atoms group together in opposite charges (positive-negative) and cancel each other out
In magnetic substances, atoms group themselves into small regions – magnetic domains – an arrange themselves randomly
When a magnet is brought near, the domains line up and the substance is attracted to the magnet
On magnets, the positive end is called North and the negative end is called South
On the Earth, the North pole has a negative charge and the south pole has a positive charge

4. What do Magnets Attract?
Non-metallic objects are not attracted
Not all metallic objects are attracted
Only iron, nickel, cobalt are attracted
Some combinations of metals are attracted
Iron, aluminum, nickel, cobalt mixed together
Aluminum on its own is not magnetic
(Events 6-A and 6-B)

5. Magnetism is a Force Magnetism is a force
Magnets have a magnetic field and it is a force that attracts magnetic substances
Event 6-C shows how iron filings will line up along this force
Unlike poles are attracted (N and S) and like poles are repelled
This magnetic field acts through certain materials (i.e. paper, glass, copper, wood, aluminum foil) and is blocked by others (i.e. iron, steel)
Any material that is magnetic will block the line of force
Event 6-D

6. Temporary and Permanent Magnets
Temporary magnets (Electromagnets)
The magnetic force can be turned on and off using an electric current
Permanent magnets
Stay magnetic for long periods of time if handled carefully
Lose magnetism by:
Placing it in a powerful external magnetic field
Heating it too much
Hitting or dropping it

7. How to Make a Permanent Magnet
Materials:
Hard steel (i.e. hacksaw blade, sewing needle, darning needle, workshop file)
Magnet
Methods:
Hold the hard steel and stroke it 20 – 30 times with a magnet

8. How to Make a Compass Materials: Methods: Magnetized needle Cork
Plastic or glass container
Water or oil
Methods:
Fill the container with the liquid, put the slice of cork in the liquid and put the needle on the cork
Observe the direction the needle moves to (N)

9. Assessment and Instruction
Students could make a compass and write a summary how it works and how they know which end points north
What can the students say about the poles of the needle? Do they use vocabulary such as magnetic poles, domains, magnetic field?
Check website listed on page 101

10. Discussion Where does this topic fit into the Science curriculum?
Which grades and strands?
Which curriculum objectives relate to the discrepant events?