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EMI qns help!

  1. Jul 2, 2011 #1
    Fig.35 shows a light and flexible conducting loop X freely hung on a smooth horizontal rail. A
    bar magnet PQ approaches the loop from the right. Which one of the following descriptions
    about this process is correct?



    A If P is a N-pole, the loop will be repelled to the left and its area will increase slightly.
    B If P is a S-pole, the loop will be attracted to the right and its area will decrease slightly.
    C No matter whether P is a N-pole or a S-pole, the loop will be repelled to the left and its area
    will increase slightly.
    D No matter whether P is a N-pole or a S-pole, the loop will be repelled to the left and its area
    will decrease slightly.

    can anyone help me with this qns? i've attached the diagram alrdy. im not sure if the area will increase or decrease. and why?
     

    Attached Files:

  2. jcsd
  3. Jul 2, 2011 #2

    Doc Al

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    Re: EMI qns help! 

    Hint: If you have two current-carrying wires next to each other, do they attract or repel? Under what conditions?
     
  4. Jul 2, 2011 #3
    Re: EMI qns help! 

    attract when the current flowing in the same direction;vice versa?
     
  5. Jul 2, 2011 #4

    Doc Al

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    Re: EMI qns help! 

    Good. So how does that relate to this problem?
     
  6. Jul 2, 2011 #5
    Re: EMI qns help! 

    if the current repels the area increase? current attract area decrease? but idk how to relate to tis qns
     
  7. Jul 2, 2011 #6

    Doc Al

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    Re: EMI qns help! 

    Consider the induced current in the loop as the magnetic flux through the loop changes.
     
  8. Jul 2, 2011 #7
    Re: EMI qns help! 

    the induced current will be in the direction to oppose the motion. - repel the approaching magnet. means area increase?
     
  9. Jul 2, 2011 #8

    Doc Al

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    Staff: Mentor

    Re: EMI qns help! 

    Good.
    Yes, but why? (Not for the reason above.)
     
  10. Jul 2, 2011 #9
    Re: EMI qns help! 

    if it repels the magnet. the area of the loop will widen and increase as if they are like straight conductors
     
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