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Homework Help: Question regarding displacement current

  1. Mar 18, 2014 #1


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    Gold Member

    1. The problem statement, all variables and given/known data
    Displacement current arises due to
    a)changing electric field
    b)changing magnetic field

    2. Relevant equations

    3. The attempt at a solution
    I think the answer should be c) because we already know that changing electric field is responsible for displacement current. But if the magnetic field is also time-dependent then it will induce an electric field according to Faraday's law. So, the induced electric field will also contribute to the displacement current.
    However, the correct answer is a).
  2. jcsd
  3. Mar 18, 2014 #2


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    Staff: Mentor

    Others are in a far better position than I to discuss your theory, but I would make 2 comments. (1) The voltage induced in a single turn (?) of an insulating material (the dielectric) by the capacitor's charging current may be minscule. (2) Consider the special case: if you were to charge the cap from a constant-current source, the charging current would be constant and unchanging, so with di/dt =0 there would be no induced voltages anywhere.
  4. Mar 18, 2014 #3


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    I'm sorry but it's still not clear to me.
  5. Mar 18, 2014 #4

    Remember that the current displacement is only defined by the change in your polarization and your change in electric field, both with respect to time.

    The magnetic field has no effect on this value.
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