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Homework Help: Induced Current

  1. May 7, 2014 #1
    1. The problem statement, all variables and given/known data
    In which of the following will a current NOT be induced in the conducting loop?

    a. Magnet moving toward upright conducting loop of wire
    b. Magnet moving away from an upright conducting loop of wire
    c. Magnet moving toward a horizontal conducting loop of wire
    d. Conducting loop of wire rotating in front of magnet
    e. Magnet rotating in front of conducting loop of wire

    2. The attempt at a solution
    I eliminated d because the loop is being rotated and that should trigger induced current, right?
    a, b, and c seem like they would have induced current because the loop is moved into or out of the magnetic field, with either the magnet moving.

    So I know that when the loop is rotated, there is induced current, but is that the same for a rotated magnet? If a rotated magnet does not trigger induced current, then would e be the correct answer?
  2. jcsd
  3. May 8, 2014 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    You need to go back to basics - how is a current induced in a loop: what has to happen as far as the magnetic field inside the loop is concerned?

    I also think you need to take a closer look at what difference it makes if the loop is "upright" or "horizontal" for the purpose of this question.
  4. May 8, 2014 #3
    Remember that induced currents are caused by a changing magnetic flux. Knowing that, do any of the solutions present a situation where there isn't a change in flux or there is no flux at all?
  5. May 8, 2014 #4
    The magnetic field must either increase or decrease. If there is no change, there will be no current.

    Okay I can see where this is getting at.. I think I need to review my right hand rules as well while I'm at it... Thank you!
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