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Homework Help: North Pole Entering a coil wound counterclockwise

  1. Jan 3, 2013 #1
    Electricity and Magnetism (Polarity)

    1. The problem statement, all variables and given/known data

    Draw and indicate the current flow for the following situtions

    a) A north pole entering a coil wound counterclockwise

    b) A north pole exiting a coil wound counterclockwise

    Also is you could please explain coils, and clockwise and counterclockwise and them realating to coils. Thanks in advance
    Last edited: Jan 3, 2013
  2. jcsd
  3. Jan 3, 2013 #2

    Simon Bridge

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    Science Advisor
    Homework Helper

    Welcome to PF;
    You should really show us how you are thinking about this problem - what resources you have tried in sorting out your ideas - that kind of thing.

    The rule you are looking for is this:
    The change in magnetic field induces an electric current whose own magnetic field opposes the change.

    Thus - the coil will try to make an electromagnet to oppose the motion of the permanent magnet. Thus - a north pole approaching induces a north pole, and a north pole leaving induces a south pole.

    The relationship between the poles and the windings of an electromagnet are available online: eg.


    ... you have to be careful about which way the current goes in relation to which way the wire is wound on the coil ... trace how the current has to flow through the wire to see.
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