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I was wondering if there is such a thing as electromagnetic induction for non closed loops. As far as I've been taught, Faraday's law applies only to closed loops, which makes me wonder how come an inductor (which is obviously not a closed loop) or a circuit with a capacitor (not really a closed loop either) can actually be induced (either self induced or mutually induced by an external source).

Thanks.

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  • $\begingroup$ Induction applies to any wire or conductor of any shape. Loops only make it more efficient by multiplying the resulting voltage by the number of loops. $\endgroup$
    – safesphere
    Sep 1, 2017 at 19:49
  • $\begingroup$ @safesphere As far as I can tell an inductor is not comprised of a single closed loop, if that's what you're referring to. $\endgroup$
    – GoingWeb
    Sep 1, 2017 at 20:58

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The loop which is referred to in the integral form of Faraday's law is not a physical structure like a wire - it is a path through space along which you are integrating the tangential component of the electric field.

When dealing with a circuit which includes a capacitor, the current does not traverse the gap between the capacitor plates, but your path of integration has no such restriction.


It should be noted that Faraday's law does not directly refer to an EMF - this comes into play when you assume that the closed loop in question refers to an infinitely thin conducting wire, and that the velocity of the charges is equal to the velocity of the wire. See the wikipedia article here for more.

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  • $\begingroup$ Sounds reasonable. May I ask for a reference to this claim? $\endgroup$
    – GoingWeb
    Sep 1, 2017 at 20:57
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    $\begingroup$ I've edited my answer to include a link to the relevant wikipedia article. $\endgroup$
    – J. Murray
    Sep 1, 2017 at 21:16

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