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Homework Help: Electromagnetic induction of copper ring

  1. Apr 28, 2008 #1
    [SOLVED] Electromagnetic induction

    1. The problem statement, all variables and given/known data
    You are given the following apparatus: copper ring, battery, variable resistor, lengths of insulated copper wire with connecting terminals at each end.
    Describe, how you would use all of this apparatus to induce a current in the copper ring.

    3. The attempt at a solution
    See the attachment for the right answer and for what I would say.

    I would say that the wire does not need to touch the loop because by altering the resistance, current changes so magnetic field changes through the loop. This change in magnetic field changes the magnetic flux. Since the rate of change of flux through loop is proportional to emf, current would be produced in the copper loop.

    Please, say your opinion to my attempt at a solution.

    Attached Files:

  2. jcsd
  3. Apr 30, 2008 #2


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    Yes, but you forgot to mention that the current must be varying to induce the current in the loop. If the current was DC, the hoop might become a static electromagnetic but no current would flow in the ring until the rate of change of magnetic flux becomes nonzero. That means that when the circut was energized or deenergized, a transient electrical pulse would be observed in a DC system.

    In an AC system, the current changes direction 50 to 60 times a second and a 50 or 60 Hz current would be induced in the ring.
  4. May 1, 2008 #3
    Yes, sure. I completely agree with you.
    Thank you!
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