What is magnetism? Force of attraction or repulsion due to
electron arrangement Magnetic forces are the strongest at the poles
Magnets have two poles: North and South
Slide 3
Magnetic poles and fields Magnets always have two poles If a
magnet is cut it will still have two poles Like magnetic poles
repel Unlike magnetic poles attract A magnetic field is the area in
which magnetic forces act
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Magnetic materials Natural magnets have naturally occurring
magnetic properties ex: LODESTONE (magnetite)
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Temporary magnets Easy to magnetize Lose their magnetism
quickly Ex: Soft iron
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Permanent magnets Hard to magnetize Stay magnetized longer than
temporary magnets Ex: alnico (cobalt, nickel, aluminum)
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Earths magnetic properties Gilbert was a scientist that showed
that the Earth behaves as a magnet The Earths magnetic field is
strongest at the poles Earths magnetic field is called the
magnetosphere
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Compasses Compasses are used to determine direction Compass
needles are magnetized and respond to the magnetic field of the
Earth Compasses point to the Magnetic Poles Of The Earth
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Other sources of magnetism Magnetic fields of the Earth and
other planets are related to their cores The sun is a source of a
magnetic field
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Magnetic variation Magnetic poles of the Earth are different
from the geographic poles of the Earth Magnetic poles shift
positions; geographic poles are constant
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Magnetic Induction Process by which materials can be
magnetized
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What affects magnetic properties? Spinning electrons cause some
metals to have magnetic properties Magnetic domains are groups of
arranged magnetic fields Dropping, hammering or heating a magnet
will cause a magnet to lose magnetic properties
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Linking Magnetism & Electricity
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Electromagnetism Discovered by Oersted (scientist) Relationship
between electricity and magnetism
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Electromagnets Temporary magnets Magnetism can be turned on and
off Made by wrapping wire around a piece of iron and sending a
current through the wire Magnetic field is in the same direction as
the electric current
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Electromagnets
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Increasing the strength of electromagnets Increasing the
voltage or current Increasing the number of loops of wire
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Electric motors vs. generators Electric motors convert
electricity to mechanical energy in order to do work Generators
convert mechanical energy to electrical energy
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Generators
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Transformers Used to increase or decrease voltage Made of
primary and secondary coils
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Transformers Two types of transformers: Step-up (increase
voltage) Step-down(decrease voltage)
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Questions What two forces are involved in magnetism? Attraction
& Repulsion Which subatomic particle accounts for magnetism?
electrons
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Questions Explain the interaction between magnetic poles when
they are close together. Like magnetic poles repel Unlike magnetic
poles attract
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Questions How is a temporary magnet different from a permanent
magnet? Temporary magnets are easy to magnetize & lose their
magnetism quickly Give an example of a natural magnet.
Lodestone
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Questions Which scientist described the Earths magnetic
properties? Gilbert
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Questions Name the devices used to indicate geographic
direction based on the Earths magnetic field. Compasses
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Questions What is the name of the Earths magnetic field?
Magnetosphere Where is the Earths magnetic field the strongest? At
the poles
Slide 28
Questions Explain magnetic variation. Magnetic poles of the
Earth are different from the geographic poles of the Earth Magnetic
poles shift positions; geographic poles are constant
Slide 29
Questions What is electromagnetism? Relationship between
electricity and magnetism Who discovered electromagnetism?
Oersted
Slide 30
Questions Name two ways to increase the strength of an
electromagnet. Increasing the voltage or current Increasing the
number of loops of wire
Slide 31
Questions What type of magnet is an electromagnet? Temporary
magnets Magnetism can be turned on and off Made by wrapping wire
around a piece of iron and sending a current through the wire
Magnetic field is in the same direction as the electric
current
Slide 32
Questions How is a generator different from an electric motor?
Electric motors convert electricity to mechanical energy in order
to do work Generators convert mechanical energy to electrical
energy
Slide 33
Questions Name two types of transformers. How is a step-up
transformer different from a step down transformer? Step-up
(increase voltage) Step-down(decrease voltage)
Slide 34
Questions What are the two parts of a transformer? A coil
Windings + An AC Source
