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

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Presentation on theme: "Basic Magnetism. Magnets occur naturally within rocks like lodestone. The word magnet is derived form a place called Magnesia because magnetic rocks are."— Presentation transcript:

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.


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