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Electromagnetism - Motor Question

  1. Feb 25, 2012 #1

    I have a very basic question.

    When a current carrying rectangular loop of wire is kept parallel to a magnetic field there is a torque in the loop of wire causing it to rotate. I was wondering what causes it to rotate further when the rectangular loop of wire is perpendicular to the magnetic field. Because the torque is no longer there when the loop is perpendicular to the magnetic field.

    Thanks. Appreciate if anyone could help me out.
  2. jcsd
  3. Feb 26, 2012 #2


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    Staff: Mentor

  4. Feb 26, 2012 #3


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    Gold Member

    The kinetic energy stored in the rotor causes it to continue to rotate. Obviously this is not going to keep going for ever, so some sort of switching is required, either an AC field, or a commutator.
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