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Effect of EMF in a wire as opposed to a metal chassis?

  1. Jan 13, 2017 #1
    Hi,
    Consider a wire with a pulsating DC current next to another wire. The expanding and contraction magnetic field induces a current into the second wire.

    Consider the same but in the second case we have a metal chassis. I assume the same magnetic field is inducing a current into the chassis.

    Is the induced current dissipated as a function of the large metal chassis and if so how? Are there other considerations?

    Thanks,

    Billy
     
  2. jcsd
  3. Jan 13, 2017 #2

    nsaspook

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    The effect is usually called a eddy current. Pulsating DC is no longer simply DC, it has a fundamental component and harmonics. For a non-zero conductance it generates heat and electromagnetic forces.

     
    Last edited: Jan 13, 2017
  4. Jan 13, 2017 #3

    davenn

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    yes, think, iron core of a transformer
     
  5. Jan 13, 2017 #4

    Baluncore

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    The same current will be induced in the chassis as in a single parallel wire. But the relatively large area of the chassis means that it has a much lower resistance than a wire, so Ohms law says a much lower voltage difference will appear along the chassis than would appear along a parallel wire.

    At radio frequencies a conductive chassis makes an excellent mirror. The current in a wire near the “ground plane” sees it's own reflection behind that reflective surface, but with a current flowing in the reverse direction.

    A “third” wire near a ground plane will be affected by both the “first” wire and by it's reflection with the opposite direction current. The current induced in a third wire will therefore be less in the presence of the chassis than with the first wire alone.
     
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