Warm Up:

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Warm Up
Create a hypothesis for the following
question Where does magnetism come from? (here,
Ill give you a hint, it involves the last couple
of chapters we have been discussing)
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MAGNETISM
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Objectives Key Questions

• Objectives
• Learn about the origins of magnetism
• Discuss the relationship between magnetism and
  electricity

• Key Questions
• Where does magnetism come from?
• How does magnetism effect your everyday life?
• What are some practical uses of magnets?
• Whats the deal with this whole Earth magnet
  thingy?!

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Misconceptions

• By breaking a magnet in two, you will isolate a
  north pole or a south pole
• The Earths magnetic field is very strong
• Like in movies, magnetism can pull things
  constantly from a far distance (Think of the
  movie Wild Wild West)

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A Brief History Magnetism

• Magnetism was discovered in Lodestones Natural
  magnets found in Magnesia, Greece.
• Often the subject of curiosity and eventually
  were used as devices for navigation.

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A Brief History of Magnetism

• Charles Coulomb (Yes, that same guy who stole
  Newtons Law!!!) studied lodestones and the
  forces between them
• -They contain pieces of iron ore called
  magnetite

Hans Christian Oersted was the first man to
discover the relationship between magnetism and
electric current.
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Question
What are the similarities and differences between
magnetism and electric charges?
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Strength of a Magnet
What effects the strength of a magnet?
Try holding the bar closer and closer to the
magnet with out letting it touch, what do you
notice about the strength of a magnet, as you get
closer? What is this similar to?

• As distance increases, field strength decreases
  (Inverse Square!!).
• As pole strength increases, field strength
  increases.

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Poles
What do we already know about poles? Has the
word come up already?
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Magnetic Poles

• Every magnet has a north and a south pole
• How are poles similar to electric charges?
• Like poles repel
• Unlike poles attract

• But how are they different?

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Breaking a magnet
What will happen if you break a magnet in two?
With the two magnets, try attaching different
ends of each magnet and record what happens.
What do you think will happen if Mr. Stief breaks
a magnet and try this again but with the two
broken pieces?
What happens? What does this say about magnetic
poles?
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Breaking a magnet

• Unlike charges, magnetic poles ALWAYS come in
  pairs

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Origin of magnetism
Where does magnetism come from?
Magnetism comes from the movement of electric
charges. Any time electric charges more, a
magnetic field forms. This can be from spinning
charges or traveling charges.
When an atom has more movement of electrons in
one direction then another, you get a net
magnetic field. Atoms that have equal amounts of
movement in all directions are magnetically
neutral.
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What have Natural Poles?
So this means that even atoms can be like tiny
little magnets.

• Metals like iron, nickel and cobalt can be
  natural magnets
• Due to a net number of electrons spinning in the
  same direction, these metals have natural
  magnetic dipole moments.
• Iron is the strongest

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Magnetic Domains
A domain is a cluster of magnetic atoms that have
aligned to form a small magnetic dipole (the
little arrows on the picture)
Domains are like tiny magnets
When all of the domains in a material start to
point in the same direction you get a magnet
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Field Lines
Pour out some iron shavings onto a tray while
holding a bar magnet underneath it. What happens
to the filings? Draw this Why does
this happen? How is it similar/different to
other concepts we have discussed in this class?
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Field lines

• Just like with electric charges, field lines can
  also be drawn for magnets.
• A great way to actually see field lines is to use
  iron filings.

Magnetic fields also have direction (just like
electric fields). They flow from North to South
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Creating a magnet
Paper Clips Try picking up a paper clip by just
touching the one in your hand to one on your
desk. Does this work? Are paper clips magnets?
Paper clip and magnet Now connect your paper
clip to your magnet and try it again. What
happens? Why do you think this happens?
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Creating Magnets
Pennies Try this again but instead of paper
clips, use a couple of pennies. Are pennies
magnetic?
Make a hypothesis as to why your materials
behaved this way.
Only some materials are ferromagnetic (They have
many domains and are able to magnetized).
Materials that arent ferromagnetic dont have
many/any domains. Copper is not a ferromagnetic
material.
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1st Method for creating a magnet
There are a number of way to align the domains in
a material. Based on the paper clip activity, we
already know one.

• By placing non-magnetized metals against or near
  a magnet, the domains in the non-magnetized
  material will line up and a net magnetic moment
• will form

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2nd and 3rd ways

1. By rubbing a material with unaligned domains with
   a magnet, the domains will align themselves,
   forming a magnet.

1. One of the best ways is to heat the material
   (like the magma from the mid-atlantic ridge) and
   then pass it through a magnetic field. When the
   material cools, its domains will have settled in
   an aligned fashion.

Permanent Magnet When the domains in a material
are able to stay aligned for a long amount of
time. Always keeps its magnetic properties even
when it is not near other magnets.
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Planets!

• -Earth, as well as other planets, have natural
  magnetic fields.
• This can be noticed by the fact that for hundreds
  of years people have used compasses to navigate.
  

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Compasses
A compass is a tool that aligns itself with the
magnetic field of earth with its north pole
pointing towards Earths Magnetic South pole.
People, however, might take the earths magnetic
field for granted what's the point?
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Earths Magnetic Field
The sun constantly bombards the earth with
dangerous charged particles.
Without the Earths Magnetic field, we would
constantly be exposed to these particles they
would kill us BUT the earths field spins these
particles to our poles along its magnetic field
lines protecting us!
Not only that from this we also get
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Earths Magnetic Field

• Auroras!

Also called the northern lights (Aurora Borealis)
Also happens at the south pole (Aurora
Australis)
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Aurora

• This occurs when the charged particles make
  contact with the atmosphere.
• This happens on other planets as well!

Aurora on Saturn
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Back to Earths Magnetic Field

• Why does the magnetic field on earth occur?
• The most common theory as to why Earth has a
  magnetic field is the fact that Earth is not a
  solid rock, but it has flowing currents of magma
  underneath its surface.

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Earths Magnetic Field

• Convection currents in the Earth make the
  magnetic field.
• Also, as the magma sloshes back and forth, the
  magnetic field switch direction over long periods
  of time.
• This has happened more than 20 times in the past
  5,000,000 years

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Evidence?

• The Mid Atlantic Ridge
• Stripes in the rock along the ridge show how
  magnetic domains were oriented when the magma
  rose form the Earths core.

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Practical Uses

• Compass
• Motors/ Generators
• Meters
• Maglev Trains
• Televisions

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Magnetism and Electricity

• When charges flow through a wire they also
  generate a magnetic field around the wire.

Changing the direction of the current changes the
direction of the field.
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Electromagnets

• An electromagnet can be made by coiling a wire
  and then passing a current through the wire. When
  coiled around a bar of iron this works even
  better since it aligns the domains in the iron.

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Uses for electromagnets

• Maglev Trains, MRI, Construction, Particle
  accelerators, etc.

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Charges and Magnetic Fields

• If a charge moves in relation to a magnetic
  field, the field will exert a force on the charge

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Forces Continued

• A current-carrying wire is also deflected by a
  magnetic field.

• Direction of current determines direction of
  force.

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Meters

• An ammeter works by passing a placing an
  electromagnet in a permanent magnet's field.
• These work in a similar way.

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DC Motor

• Motors us these principles to work as well