Electromagnetism (S8P5 b, c)

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Electromagnetism(S8P5 b, c)

• Physical Science
• Candace Black
• Spring, 2010

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Electric Current and Magnetism
Can you identify the 3 necessary parts of a
circuit?

• Electric current produces a magnetic field.
• The relationship between electricity and
  magnetism is called electromagnetism

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Solenoids

• 3 characteristics of magnetic field
  
• produced by current
• 1. Can be turned on or off.
• 2. Direction can be reversed.
• 3. Strength can be changed.
• A coil of wire with a current is called a
  solenoid.

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Electromagnets

• A solenoid with a ferromagnetic core is called
  and electromagnet.
• Magnetic field is produced by both the current in
  the wire and the magnetized core.
• A strong magnet that can be turned on and off.
• Increase strength by
• 1. Increasing current
• 2. Add more loops
• 3. Place coils closer together
• 4. Use stronger ferromagnetic material
  as core.

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Uses of Electromagnets

• Audiotapes, videotapes, computer hard drives,
  credit cards
• Doorbell
• Fire doors(be able to explain how these work in
  our school)
• To lift heavy objects such as junk cars, metal
  containers such as are used in shipping, etc.

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Electric Motors

• A device that uses an electric current to turn an
  axle.
• Transforms electrical energy into mechanical
  energy.

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In your notes, write at least 3 things that you
can think of that use motors.
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Induction of Current

• Electric current is induced in a conductor when
  the conductor moves through a magnetic field.
• Generating an electric current from the motion of
  a conductor through a magnetic field is called
  electromagnetic induction.
• Current that is generated in this way is called
  induced current.

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Induced Currents

• A current consisting of charges that flow in one
  direction only is called a direct current or DC.
• Example battery operated items charges flow
  from positive end through circuit back to
  negative end.

• A current that flows back and forth in a circuit
  is called an alternating current or AC.
• Example homes, buildings, schools,
• Advantage voltage can be raised or lowered
  higher voltages can travel over longer distances
  (from power plant) then can be lowered for
  everyday use (in our homes).

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Generators

• An electric generator is a device that transforms
  mechanical energy into electrical energy.
• A generator uses motion in a magnetic field to
  produce an electric current.
• Electric motors use and electric current in a
  magnetic field to produce motion.
• Generators are used in power plants with turbines
  acting as the crank.

Be able to compare/contrast generators and motors.
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Transformers

• A transformer is a device that increases or
  decreases voltage. (voltage is?)
• Consists of 2 separate coils of insulated wire
  wrapped around an iron core.
• Two types of transformers are
• 1. step-up transformer increases
• voltage.
• 2. step-down transformer decreases
• voltage.

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???????????
What are your questions?