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Using Lenz's Law

  1. Oct 14, 2008 #1
    1. The problem statement, all variables and given/known data
    Use Lenz's law to determine whether the induced current in the resistor R is from A to B or from B to A in the following configurations:

    (1) a magnet with south side pointing down is entering a coil attached to a resistor with A coming before B if you go clockwise

    (2) a magnet with north side leaving a coil attached to above resistor

    (3) a magnet with north side entering the above coil

    (4) a magnet with south side entering the coil like above but it is flipped (like it is starting to wind from bottom instead of top)

    2. The attempt at a solution

    I tried using the Right Hand Rule but I'm not sure exactly what to do. Like for the first one, since the south side is entering the coil, the magnetic field would be from south to north (?) so then the current would be counterclockwise..since it is entering, it would want to oppose and the induced current is clockwise?? so it is from A to B?

    For the second one since it is leaving, it would want to stay the same so it would be counterclockwise and be from B to A?

    and the third one since it is north entering, the field is pointing down so it is clockwise, and would want to oppose so becomes counterclockwise??

    and last one I'm not sure how the change in which side the coil starts to wind even effects the current at all? so it would be same as the first one A to B??
  2. jcsd
  3. Oct 15, 2008 #2


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    Is there supposed to be a picture for this question? It's hard to visualise the problem.
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