1. Basic Magnetism

2. Magnets occur naturally within rocks like lodestone. The word magnet is derived form a place called Magnesia because magnetic rocks are common there.

3. Types of Magnets Permanent – retain magnetism permanently

4. Types of Magnets 2. Electromagnets – when an iron bar is wrapped with a current carrying wire, the bar becomes a magnet. It ceases to be magnetic when the current is off.

5. Types of Magnets 3. Solenoid – A coil of wire itself exhibits magnetism when the current is on.

6. Lines of Force In all cases, the magnet produces magnetic lines of force that attract or repel other magnets. The magnetic lines of force form a magnetic field. All lines are said to originate at the N pole and travel to the S. (You may also consider the lines to point in the direction that an N pole test magnet would be pushed.)

7. Lines of Force

8. The Greeks found a rock (magnetite or lodestone) that attracted iron. The Chinese used this to invent compasses in the 11 th century.

9. A few materials (iron, steel) are strongly attracted to magnets. Others are less strongly (cobalt, and nickel).

10. Types of Magnetism Ferromagnetic – materials with a strong magnetic attraction. (iron, steel) Paramagnetic – materials with a slight magnetic attraction. (wood, aluminum, platinum, oxygen) Diamagnetic – weakly repelled by strong magnets. (zinc, bismuth, sodium chloride, gold)

11. Theory of Magnetism Magnetism is a property of a charge in motion. The electrons revolve around the nucleus, causing the magnetism. The electrons also spin on their own axis (like the Earth), producing a magnetic field. However, when the electrons are paired, the fields cancel each other out.

12. Domains Domains are regions of magnetic substances that have a free, spinning electron. When these domains line up, the substance becomes a magnet.

13. Evidence that supports the domain theory 1.Rubbing a nail with a magnet turns the nail into a magnet. 2.Rubbing a test tube of iron filings produces North & South poles that can be seen with a compass. 3.When temporary magnets are hit, they lose their magnetism.

14. Evidence that supports the domain theory 4.Breaking a magnet in two, results in 2 magnets with North & South poles.

15. Evidence that supports the domain theory 5. The magnetism of a bar magnet can be reversed by a strong external magnetic field.