CHPT 2 NOTES 
MAGNETISM
I. Magnetism makes our planet able to support life:
	A. Van Allen Belts -- magnetic force lines around the Earth 
		1. solar wind -- charged solar particles (form of radiation)
		2. life possible here because we don't get hit with intense radiation
	B Astrobiology - the study of life in other parts of the universe
		1. Evidence for ET life -- Meteor found in Antarctica is from Mars and has
	 	magnetite crystals that look just like the crystals we see in some Earth 
		bacteria. This means that there may be bacterial life on Mars similar to 
		ours.
	

II. Magnets - All magnets have N and S poles.
	A. What we have learned from experiments:
		1. When free to move, magnets line up along magnetic force lines, N & S
		2.  Magnets can sometimes magnetize other metals.
		3. RULE: 	Like poles repel
				Opposite poles attract
		4. Not all metals are magnetic
		5. Magnetism still works through paper
		6. See pg 53, 55 & 56 for illustrations of magnetic fields
		7. Magnetic force is strongest at the poles
		8. When you break a magnet, you get 2 whole new magnets (N-S & N-S)

	B. History -- Lodestone  - naturally magnetic rocks
		1. discovered by the Greeks. 
		2.  now called magnetite (Fe O )
	
	C. Compass -- Made of a magnet
		1. Usually lines up N & S with the magnetic force lines of the Earth 
		2. See diagram on pg 52
		3.  If a compass is near a strong magnet, it will line up with that magnet's
			magnetic force lines. (see diagram on pg 52 - 53)
	
III. Magnetic Domain Theory -- Magnetism is caused by tiny magnetic regions all lining up the same way on the molecular level.
	

	


		magnetized iron			       unmagnetized iron



IV. Induced Magnetism -- When an unmagnetized object is brought near a strong magnetic field, its domains will all line up and it will become a magnet
	A. ALNICO -- an alloy made of Aluminum, Nickel and Cobalt that makes good
		permanent magnets.
	B. Electromagnets -- A current-carrying wire creates a N & S pole. Its magnetism
		can be turned off.
		1. more coils = more magnetism
		2. more volts = more magnetism
		3. iron core = more magnetism

V. Loudspeakers use an electric coil and a permanent  magnet to vibrate a paper cone. This produces sound.


s   NN						paper cone

						When electricity changes direction, it reverses
						the N & S of its electromagnetic field.
magnet					(Then it pushes and pulls the paper  cone,
						producing sound.)

VI. Electric Motor -- device that changes electrical Energy to motion (mechanical E)
																		rotating coil is called an armature							
commutator				N	
changes direction											
of current				N				permanent magnet

					S

								 														source of electricity


VII. Transformer -- device that increases or decreases voltage
	A. Step up -- when small # of coils lead to large # of coils, this increases voltage
	 (Ex: for neon sign)
	 
120 V								  240 V
in----->                  						 ----> output


	Primary coils	 (100 wraps)		Secondary coils  (200 wraps)
	 

	B. Step down -- when large # of coils lead to small #of coils, this decreases 
		voltage (Ex: toy trains)

	120 V							  6 V
	input								output
			Primary coils		Secondary coils
			(100 wraps)		(5 wraps)
VIII. Electric Generator --  a device that uses a magnet to change mechanical energy to electric Energy.
A.  Electric currents can be measured by these devices:
	1. ammeter measures amps
	2. galvanometer measures small amp levels
	3. voltmeter measures volts

B. When a coil moves through a magnetic field an induced electric current is produced					
					N	
																S