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Picture two coils in close proximity. They have the same dimensions and are located co-axially, with a small gap between then (like Helmholtz coils, but much closer together than in the standard configuration). They are not electrically connected.

Now, I want to measure the self-inductance of one of the coils, so I connect a hand-held LCR meter. My understanding of this instrument is that it will generate a small AC current in the coil and measure L.

Is this measurement affected by the presence of the other coil, IF THE SECOND COIL IS NOT CONNECTED to anything (open terminals)?

Please see this question for reference:

When mutual inductance is occurring between two coils, is self inductance always occurring in each individual coil?

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The reason for mutual inductance is that the AC field in the test coil generates a current, and therefore an opposing magnetic field, in the second coil. That is what cause the mutual inductance. In this case, since the coil terminals of the second coil are open, no current can flow in it. Therefore, there is no interaction between the coils and the self-inductance measurement is not affected by the second coil.

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  • $\begingroup$ This assumes you're well below the self resonant frequency of the second coil. If you're not, a significant capacitive displacement current will flow even if the terminals are open. $\endgroup$
    – John Doty
    Commented Feb 3, 2023 at 23:35
  • $\begingroup$ Understand. Measurement frequency is 1 kHz. I will try to estimate the resonance frequency of the second coil. $\endgroup$
    – germ
    Commented Feb 4, 2023 at 3:54
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    $\begingroup$ the resonance of the second coil will be in the megahertz range. If driven at this frequency, the coupling between the coils will be very strong. at 1 kilohertz, negligible. $\endgroup$
    – niels nielsen
    Commented Feb 4, 2023 at 5:52

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