Download 18.1 - Pierce Public Schools

Ch. 18 Magnets
18.1
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Magnets any material that attracts iron or any material containing iron
Poles part of magnet where magnetic effect strongest
North (N) attracts South (S) (opposites attract)
N/N or S/S repel
Magnetic force force of repulsion or attraction between poles
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Magnetic field area around poles where magnetic force acts
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Iron, Nickel, Cobalt only elements that can be magnetic
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o Reason: e- in most atoms exist in pairs with each e- spinning in
opposite directions (each e- causes magnetic field around it) most
materials are cancelled out by opposite fields) Fe, Co, Ni have
unpaired e- that have no cancellation (each atom a very small
magnet)
o Magnetic field created by each iron atom exerting force on others
atoms, causing groups of atoms to align to their magnetic poles so
all alike poles facing same direction. This group of atoms called
magnetic domain.
Two types of magnets
o Permanent magnets a magnet that’s magnetic domain fixed
o Temporary magnet a magnet that’s magnetic domain is aligned
for short period of time
 Electromagnet current is passed thru a coil and a
stronger temporary magnet is formed
 Increase magnetism by:
o Adding more coils
o Adding more current
o Making core bigger
 Ex. Doorbells, loudspeakers, carlifts
 Nail rubbed with permanent magnet in same direction
Earth’s North pole has a South polarity
Earth’s magnetic field created by liquid outer core spinning
Auroras result of solar winds hitting magnetic field and directed to the
North and South Pole.
18.2
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Hans Christian Oersted discovered electromagnetism ( interaction between
electricity and magnetism
o Compass changed position when electric current was going thru a
wire
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o 3 parts to an electromagnet
 solenoid wire in a tight coil
 iron core
 energy source
Electic motor device that changes electrical energy into KE
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armature loops or coils of wire that can rotate
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commutator device attached to armature to reverse direction of electric
current
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18. 3
galvanometer device used to detect current (calibrated to measure
potential difference or current)
o ammeter current
o voltmeter potential difference
o Michael Faraday
o Electromagnetic inductionchanging magnetic field through a wire
produced electric current
o Generator device that uses electromagnetic induction to convert
KE into electrical energy
 AC (alternating current)
o Transformer device that increases or decreases the voltage of an
alternating current
 Step downprimary coil has more coils than secondary coil
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Step up secondary coil has more coils than primary coil