1. What have we learned from the labs?
Magnets and Magnetism
What have we learned from the labs?

2. Activity: What kinds of objects are attracted to a magnet?
Iron, nickel, cobalt and alloys containing these elements are attracted to a magnet.

3. Diamagnetic have a weak, negative susceptibility to magnetic fields.
slightly repelled by a magnetic field
does not retain the magnetic properties when the external field is removed
most elements in the periodic table, including copper, silver, and gold

4. Paramagnetic have a small, positive susceptibility to magnetic fields
slightly attracted by a magnetic field
does not retain the magnetic properties when the external field is removed
magnesium, molybdenum, lithium, and tantalum

5. ferromagnetic
have a large, positive susceptibility to an external magnetic field
exhibit a strong attraction to magnetic fields
able to retain their magnetic properties after the external field has been removed
strong magnetic properties due to the presence of magnetic domains
iron, nickel, and cobalt

6. Activity: How can the strength of magnets be compared
Different methods can be used to compare the strength of different magnets. They can used to pick up paper clips and the number of paper clips picked up by the magnet can be compared.

7. Activity: Where is a magnet strongest?
A magnet is strongest at the poles.
A magnet has two poles – north pole and south pole.

8. More on Magnet’s poles
When a magnet is broken into smaller pieces, each small piece will have its own north and south poles.

9. Activity: Which way is north?
The north direction is when the directional compass points
The north pole of a bar magnet points in the north direction.
A compass needle is a small bar magnet.

10. Activity: How do magnets affect one another?
Unlike poles attract, like poles repel.

11. Earth’s poles
If like poles repel and unlike poles attract, why is the north pole of a bar magnet pointing towards the north direction? Does this violate the law of magnetic poles?

12. Earth’s poles
Earth has two poles, magnetic and geographic.

13. Earth’s poles

14. So what is the cause of all magnetism?
Moving charges
Electrons circling the nucleus of an atom cause magnetism
In most substances, equal numbers of electrons spin in opposite directions, which cancels out their magnetism. 
In substances such as iron, cobalt, and nickel, most of the electrons spin in the same direction. This makes the atoms in these substances strongly magnetic.

15. Magnetic domains
The strength of the magnet depends on the arrangement of the magnetic domains of the magnet
Magnetic domains are regions of 1012 to 1015 atoms
when magnetic moments of these atoms are aligned parallel the material is said to be “magnetized”

16. Magnetic domains