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Homework Help: Mutual Fluxes and Lenz's law

  1. Mar 9, 2016 #1

    1. The problem statement, all variables and given/known data
    All variables and known data are given in one of the attached files.
    Does the figure 8.2 show that the current I1 is constant?

    My assumption is based on Lenz's law. What I mean is that if the I1 varies, there will be changes in magnetic fluxes(delta-B) produced by I1. The circuit C2 will oppose this change by forming its current I2; consequently, there will be fluxes, which are generated by I2, that will penetrate C1 also. Therefore, the assumption will not happen if I1 is constant.

    2. Relevant equations
    depicted in one of the attached files.

    3. The attempt at a solution
    I both study the mutual inductance in the textbook containing the following pictures and Lenz's law. Also, I try to combine them together. I just want to check my understanding.

    Attached Files:

  2. jcsd
  3. Mar 10, 2016 #2


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    Homework Helper
    Gold Member

    I'm not sure what, if anything, you are asking here, but here are my comments.

    No. I1 can vary.

    But there is nothing to stop I1 from changing. If I1 changes, then there will be an induced emf in C2 and I2 will change. The flux change caused by this will oppose the change in I1, but not prevent it. Here, there is only partial linkage between the coils, so there is plenty of stray or leakage flux which can be changed by I1. But even where there is tight coupling between the coils, unless the flux linkage is 100% and the coil C2 is a perfect conductor, the change in I2 will not be enough to completely prevent the change in I1.

    Lenz's law tells you only the sense in which induced emfs and currents act, not their magnitude.
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