Magnetism

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Magnetism

• property of matter in which there is a force of
  attraction or repulsion b/w like or unlike poles

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What do we know about magnets?

• 2 Magnetically opposite poles
• North Pole and South Pole
• Like poles repel and Opposite poles attract
• Well get back to this later

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What types of things do magnets attract?
1st

• Do magnets attract all metals?
• Magnets only attract objects made of iron,
  cobalt, or nickel!!
• These metals are called the Iron Triad
• See Periodic Table
• You can also only make a magnet out of these 3
  metals.
• Those rubber magnets have iron, cobalt or
  nickel in them.

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Magnetic Domains

• The molecules of most substances have no
  orientation to them.
• In a magnet, the molecules align themselves in a
  very specific pattern.

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Do magnets have to be touching each other in
order to have an effect on each other?
I wonder why?
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Magnetic Field

• Surrounding all magnets is a magnetic field.
• Magnetic Field is the area surrounding a magnet
  where the magnetic force acts.

Magnetic Field Lines
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Magnetic Field Lines
Magnetic Field Lines always move out of the North
pole and into the South pole!!
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What makes the North Pole the North Pole and the
South Pole the South Pole?
It is not the N and S stamped on them!!!!
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The North Pole is the pole that the magnetic
field lines move out of. The South Pole is the
pole that the magnetic field lines move into.
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Magnetic Field Lines

• Magnetic Field lines always move out of the North
  end and into the South end!!

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Magnetic Field Lines of Interacting Magnets
Lines of Attraction
Lines of Repulsion
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Solving for Unknown Poles
Are the field lines attracting or
repelling? North ____________ what?
attracts
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Solving for Unknown Poles
Are the field lines attracting or
repelling? North __attracts______ what?
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Solving for Unknown Poles
Are the field lines attracting or
repelling? North ____________ what?
repels
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Solving for Unknown Poles
Are the field lines attracting or
repelling? North __repels____ what?
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Determine the unknown pole

1. North
2. South

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Determine the unknown pole

1. North
2. South

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Where are Magnets the strongest?
I wise man told me many years ago that Magnets
are strongest at the poles. That is where the
magnetic field lines are the most concentrated.
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Which of the following metals would not make a
very good magnet?

1. Iron
2. Cobalt
3. Aluminum
4. Nickel

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What happens if you break a bar magnet in half?
Mr. Garay
You get 2 bar magnets both with a North and a
South pole!!
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Breaking a Bar Magnet
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Where is this magnet the strongest?

1. 1 only
2. 2 only
3. 3 only
4. 1 and 3

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Where is this magnet the strongest?

1. 1 only
2. 2 only
3. 3 only
4. 1 and 2

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If you broke a bar magnet in half and then broke
both halves in half again, how many bar magnets
would you have?

1. Not possible
2. 2
3. 4
4. 8

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Note-taking Skills Worksheet

• A. Magnetismthe properties and interactions of
  magnets.
• 1.Interaction b/w 2 magnets, called magnetic
  force, increases as magnets move closer together.
• 2. A magnetic field, which exerts the magnetic
  force, surrounds a magnet, and is closest to the
  magnet.

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Note-taking(cont.)

• B. Magnetic Polesthe region of a magnet where
  the magnetic force exerted by the magnet is
  strongest.
• 1. All magnets have a north and a south pole.
• 2. Like poles repel. Unlike poles attract.
• 3. Earth has magnetic poles.
• A) A compass needle is a small bar magnet that
  can freely rotate.
• B) A compass needle always points north.

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Note-taking(cont.)

• C. Magnetic materialsiron, cobalt, and nickel
• 1. The magnetic field created by each atom
  exerts a force on nearby atoms.
• 2. Magnetic domainsgroups of atoms with aligned
  magnetic poles.
• A) In a magnet, the like poles of all the domains
  point in the same direction.
• B) Permanent magnets are made by placing a
  magnetic material in a strong magnetic field,
  forcing a large number of magnetic domains to
  line up.

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Any Questions??