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Induced Current GRE Problem

  1. Sep 5, 2013 #1
    1. The problem statement, all variables and given/known data
    http://grephysics.net/ans/9277/54

    I am confused about this. The explanation for why the induced current is clockwise is because the induced current would resist the change in magnetic flux, therefore work to increase the magnetic field. But if the current induced in the wires is in the same direction as the original current, I use the right hand rule and it seems as if the magnetic field's will work to cancel eachother out.

    I'm picturing two circles going around each wire in the same direction (magnetic field) and between the wires one magnetic field will be going up while the other goes down.
    Where is my thinking going wrong here?

    Edit:
    Is it because if the current is moving in the same direction, there will be an attractive force and therefore it will fight to increase the magnetic field? I feel like this logic isn't right because everyone else seems to be deducing the fact that it is going clockwise and then use that information to decide which way the forces are pulling on each side
     
    Last edited: Sep 5, 2013
  2. jcsd
  3. Sep 5, 2013 #2

    rude man

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    That statement makes no sense. The induced current will be in the same direction as that of the long wire in one side of the loop and obviously will be in the opposite direction in the other side.

    What direction of loop current will increase the flux thru the coil? (Use the right-hand rule).

    As to why E is right and D is wrong, you can also solve this dilemma by remembering that for parallel wires, same-direction currents imply attraction while opposite-direction currents imply repulsion.
     
  4. Sep 5, 2013 #3
     
    Last edited: Sep 5, 2013
  5. Sep 5, 2013 #4

    rude man

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  6. Sep 5, 2013 #5
     
  7. Sep 5, 2013 #6
     
  8. Sep 5, 2013 #7

    rude man

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  9. Sep 5, 2013 #8

    rude man

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  10. Sep 6, 2013 #9
     
  11. Sep 6, 2013 #10

    rude man

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