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B Rotating solenoid

  1. Sep 11, 2016 #1
    In the presence of a constant magnetic field, does the action of rotating a solenoid (with a fixed amount of coils) produce an emf?

    Thank you!
  2. jcsd
  3. Sep 11, 2016 #2

    Charles Link

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    I think this is the principle behind an electric generator where an EMF gets created anytime even a single loop is rotated in a static magnetic field. It's the opposite of an electric motor where the current is run through the loop in a magnetic field and the loop gets a torque on it.
  4. Sep 11, 2016 #3


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    I agree with Charles. Why would it not?

    Do you know which equation to use to calculate the EMF in this situation?
  5. Sep 11, 2016 #4
    I was thinking about Faraday's law, where a change in magnetic flux is necessary for an induced emf.

    In this scenario, I am not sure where the changing magnetic flux comes from, since the magnetic field is constant and the area through which the magnetic field lines cross is constant, even if the solenoid itself is spinning (assuming the solenoid has radial symmetry).
  6. Sep 11, 2016 #5

    Charles Link

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    An additional comment or two for the OP: Faraday's law applies in a couple of different scenarios: 1) The loop can be static and the magnetic field (flux through the loop) increased or decreased. 2) The loop can be rotated in a static field. 3) The loop can be translated and/or be made to change in shape so that the magnetic flux through it varies. In all 3 cases, an EMF results. And to respond to your post #4, the rotation needs to be in such a manner that the magnetic flux through the loop changes in order to get an EMF. You should be able to figure out the type of rotation needed in order to get an EMF in the solenoid.
  7. Sep 11, 2016 #6
    Great, thank you!
  8. Sep 11, 2016 #7

    Charles Link

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    Just an additional comment or two: Without googling the subject of electric generators, of which the explanations with all the stator and rotor terms in the construction of the generators can be difficult to follow, I think it is fair to conclude that there are two rather simple ways to generate such an EMF (which will generate a sinusoidal (ac) EMF: 1) You can rotate the solenoid in a static magnetic field or 2) You could rotate the permanent magnet and leave the coil or solenoid stationary. Both methods should work.
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