Magnetism

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Magnetism
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Types of Magnets

• Temporary When charged particles move through
  space, they induce a magnetic field
  (Electromagnets).
• Permanent Electrons have an intrinsic magnetic
  field that may add together in certain matter to
  create a magnetic field (Speakers).

Temporary
Permanent
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In 1820, it was discovered that a compass needle
is affected by an electric current.

• Several responses to Hans Christian
  Oersted's observation
• No way!!!For realz?
• Liar!
• Unbelievable!

He went further to propose that the direction of
the field changed with the direction of the
current. 
Electric currents affect magnets. What might
affect electric currents?
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What is an ELECTROMAGNET?

• A temporary magnet made by wrapping a wire coil
  carrying a current around an iron core. 

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• Solenoid - a single wire wrapped around a cylinder

In a car or truck, the starter solenoid is part
of an automobile starting system. The starter
solenoid receives a large electric current from
the car battery and a small electric current from
the ignition switch. 
When the ignition switch is turned on, the small
electric current forces the starter solenoid to
close a pair of heavy contacts, thus relaying the
large electric current to the starter motor.
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Properties of Electromagnets

• 1. Temporary, only magnetic when there is a
  current flow
• 2.  Strength of the magnet is increased by adding
  more loops of the wire around the cylinder
• 3.  It still has a north and a south pole
• 4.  Attracts other magnetic materials
• 5.  When current is turned on, the magnet may be
  attracted (or repelled) to other magnets.  The
  movement can then be converted to mechanical
  energy to work
• Examples  
• Stereo speakers
• Electric motors
• Telephones

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Focus on SPEAKERS

• The loudspeakers in your radio, television or
  stereo system consists of a permanent magnet
  surrounding an electromagnet that is attached to
  the loudspeaker membrane or cone.

By varying the electric current through the wires
around the electromagnet, the speaker cone moves
back and forth. The resulting vibration of the
speaker cone will create sound waves, including
that from voice and music.
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Magnets Can be Used to Move ObjectsWhen you
turn off the power, the magnet stops working (and
you can drop the object)
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These same principles are used to make equipment
that can lift large objects by switching a magnet
on and off.
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What is a galvanometer?

• These are devices that are used to measure
  electric current.
• Gauges in your car use these devices to measure
  how much  gasoline is in the tank, or the water
  temperature in the engine.

A float in the fuel tank is attached to a senor
that sends a current to the gauge galvanometer.
 As the level changes, so does the current.  The
changing current causes the needle to rotate
toward empty.
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What is an electric motor?

• Device that changes electrical energy into
  mechanical energy - causing something to move
•                      -- blades of a fan
•                     -- wheels of a car
•                     --  hair dryers
•                     -- blenders

http//www.sparkmuseum.com/MOTORS.HTM
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Electric Motors - convert  electrical energy to
mechanical energy   This motor runs a current
through a wire.  The wire is then attracted and
then repelled by the magnet underneath - this
will cause it to SPIN
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How to Build a Simple Electric Motor Even
Simpler  Magnet, Wire, Battery
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What is a GENERATOR?

• Converts mechanical energy to electrical energy

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Quiz Time   - check out this page
firsthttp//www.magnet.fsu.edu/education/tutoria
ls/index.htmlCheck out the Science
Demonstrations link for some neat tricks with
magnets.Or check out this video about "LINEMEN"
who repair power lines  http//www.youtube.com/wa
tch?v7gl-_Liz_0oFaraday on PHET
http//phet.colorado.edu/en/simulation/faradays-la
w
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• 1. All magnets are surrounded by an invisible
  force called the ________________
  _______________2. The north pole of one magnet
  will be attracted to the ______ pole of another
  magnet.3. The poles of the earth can move.
  True or False?4. In the far north, radiation
  from the sun is reflected off the earth's
  magnetic field and creates patterns of colors.
  This effect is known as the ___________
  ________________5. A nail is normally not
  magnetized. How can you magnetize it?

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• 6. Who discovered that magnets are affected by
  electricity?7. You can make an
  ______________________ by wrapping a wire coil
  carrying a current around an iron core.8. What
  car part is attached to your starter and is
  needed to start the car? 9. This is a device
  used to measure electric current.10. A
  generator converts ___________ energy into
  electrical energy.