Electric Motors

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Electric Motors

• SPH4C

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Electromagnetism More Practice
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Electromagnetism More Practice
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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.

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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).

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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.

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RHR3

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

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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.

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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.)

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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.

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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

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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.     

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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.

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Building a basic DC motor

• http//www.youtube.com/watch?featureplayer_embedd
  edvP6lBvAQ9P_c