Magnetism

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Magnetism

• Chapter 21

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21.1 Magnets and Magnetic Fields
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Magnetic Forces

• Force a magnet exerts on another magnet, on iron,
  or similar matter.
• They attract or repel another magnet.
• Have 2 poles North-seeking (N) and South-seeking
  (S)
• Poles are the strongest area

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Poles ( and ) will attract to each other
  An interesting characteristic of magnets is
that when you cut a magnet into parts, each part
will have both N and S poles.
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Magnetic Field

• The region around the magnet where magnetic
  force is at. The field begins at the N pole and
  extend to the S pole.

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Magnetic Domains

• This is a groups of atoms arranged in
  unmagnetized iron. The blue arrows show their
  magnetic orientation.

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How the domains line up
When a magnet comes near the metal, the domains
align themselves towards the magnet. Notice how
the arrows have changed direction.
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21.2 Electromagnetism
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Electromagnetic Force

• A force made of electricity and magnetism.
• Caused by charged particles.

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Electromagnets

• By wrapping a wire around a nail and running an
  electrical current through the wire, you can
  magnetize the metal and make an electromagnet.

View clip
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FYI

• If the core is soft iron, the magnetism will
  diminish as soon as the current is turned off.
  This feature makes electromagnets good for
  picking up and dropping objects.

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Electric Motors

• Device that uses an electromagnet to turn an
  axle.
• Electromagnet rotates between opposite poles
  turning electrical energy into mechanical energy.

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21.3 Electrical Energy Generation and Transmission
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Electromagnet Induction

• A current is produced when a wire (conductor) is
  moved through a magnetic field.
• View clip

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Generators

• Device that converts mechanical energy to
  electrical energy
• 2 types of generators AC and DC
• View clip

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Transformers

• Device that increases or decreases energy from
  one circuit to another by magnetic coupling with
  no moving parts
• See pg. 645 647
• View clip

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The End
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Magnetic Poles

• 2 spots on the N S hemispheres that are
  situated over the magnetic poles of the Earth's
  core. A compass needle points to the north
  magnetic pole.

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Meters

• Galvanometer uses an electromagnetic to detect
  currents.
• Ammeter measures electric current (think amp)
• Voltmeter- measure potential
• difference across part of a
• circuit (think volt)

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FYI

• The magnetic compass is the only instrument in
  the aircraft by which the pilot determines the
  direction of flight.