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B Magnetic/electromagnetic induction

  1. Jul 3, 2017 #1
    Suppose there is a coil around a C-shaped iron core with a dipole magnet in the gap as shown in the dynamo below. As the magnet is spinning, in order to oppose the force, a changing pole is produced in the iron. (Eg. As N-pole approaches the iron core, a north pole is induced to oppose the movement.)

    However, if i were to recreate a similar setup with just a C-shaped iron core and a spinning dipole magnet, by magnetic induction, an unlike pole is induced.(Eg. As N-pole approaches the iron core, a S-pole is induced in order to be attracted.) Hence what i do not understand is how a coil is able cause the difference in induction of poles.
  2. jcsd
  3. Jul 3, 2017 #2


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    The coil alone does not make a difference. It is the current, if any, flowing in the coil that creates the poles opposing the movement.

    You can feel this with a dynamo. It is relatively easy to turn when the coil is not connected, but gets harder in proportion to the current drawn, when an electrical circuit is attached. Attaching a short circuit makes it hardest to turn, as this allows most current to flow.
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