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Electric Motors

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ELECTRIC MOTORS SPH4C Electromagnetism: More Practice Electromagnetism: More Practice The motor principle A device that uses an electromagnet in a permanent magnetic ... – PowerPoint PPT presentation

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Title: Electric Motors


1
Electric Motors
  • SPH4C

2
Electromagnetism More Practice
3
Electromagnetism More Practice
4
The motor principle
  • A device that uses an electromagnet in a
    permanent magnetic field to apply a directed
    force is called an electric motor .
  • It operates by the motor principle.

5
The motor principle
  • A device that uses an electromagnet in a
    permanent magnetic field to apply a directed
    force is called an electric motor .
  • It operates by the motor principle (aka RHR3).

6
The Motor Principle (aka RHR3)
  • Two magnetic fields interact with each other to
    produce a force, so a conductor that carries
    current through an existing magnetic field
    experiences a force perpendicular to both the
    current and the external magnetic field.

7
RHR3
  • The direction of the force can be determined by
    the third right hand rule.

8
Electric Motors
  • The electric motor directs electric force full
    circle, without stopping part way.
  • In a DC motor, the electromagnet has to change
    its polarity once every rotation. This polarity
    change is made because a split ring commutator
    reverses the current flow in the rotating
    armature.

9
The Simple Induction AC Motor
  • The direction of AC alternates back and forth
    anyway. (In North America, this cycles 60 times
    per second . . . which translates to rps of the
    motor.)

10
Building a basic DC motor
  • Starting about 3 inches from the end of the wire,
    wrap it about seven times around the D-cell
    battery. Remove the battery and cut the wire,
    leaving a 3 inch tail opposite the original
    starting point.

11
Building a basic DC motor
  • Wrap the two tails around the coil so that the
    coil is held together and the two tails extend
    perpendicular to the coil.
  • Note Be sure to center the two tails on either
    side of the coil. Balance is important. You might
    need to put a drop of glue where the tail meets
    the coil to prevent slipping

12
Building a basic DC motor
  • On one tail, use fine sandpaper to completely
    remove the insulation from the wire. Leave about
    1/4" of insulation on the end and where the wire
    meets to coil. On the other tail, lay the coil
    down flat and lightly sand off the insulation
    from the top half of the wire only. Again, leave
    1/4" of full insulation on the end and where the
    wire meets the coil.     

13
Building a basic DC motor
  • Place the coil in the cradle. You may have to
    give it a gentle push to get it started, but it
    should begin to spin.
  • If it doesn't spin, check to make sure that all
    of the insulation has been removed from the wire
    ends. If it spins erratically, make sure that the
    tails on the coil are centered on the sides of
    the coil.

14
Building a basic DC motor
  • http//www.youtube.com/watch?featureplayer_embedd
    edvP6lBvAQ9P_c
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