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https://youtu.be/M8aZoM9p43k

This YouTube link shows a experiment I quickly made.

Two resonant lc circuits that use magnetic fields to wirelessly light up a led. I manually found the best frequency after finding the inductance using a LCR meter. Its low frequency, so like 200kHz. No impedance matching. My two main questions are:

Is there a way to analytically solve for the power received. I know inductance, frequency, coil size, wire size, etc. Also, can you calculate for power received when a foreign similar coil is placed wirelessly in between the sending and receiving coil. If you watch the link, you see it increases power transfer. It can also decrease the power transfer. Im guessing because it changes inductance and throws off resonance. Is there a general equation for power transfer as a function of distance, inductive loops, frequency, etc.

Also, from my experiment, a square wave works much better than a sin wave and the signal received in the oscilloscope is sin wave, even though im sending a square wave. Is there math to explain the square wave working better(found experimentally) and the signal received is a sinusoid? Thank you

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  • $\begingroup$ The signal received is sinusoid for all input frequencies? $\endgroup$ – Javi Sep 4 at 3:32
  • $\begingroup$ I've only tried inputting a square wave and a sine wave. The square wave created the same sinusoid as the sine wave input, but with higher amplitude than the sine wave. And a brighter led $\endgroup$ – Chris Bolig Sep 4 at 3:35
  • $\begingroup$ Did the frequency of the received signal (sinusoid) change as you changed the input frequency of the squate wave? $\endgroup$ – Javi Sep 4 at 3:51
  • $\begingroup$ just gets lower and lower in amplitude as you vary from the frequency of the square wave. The frequency was constant. I believe its a lc tank where its a band pass filter. The received signal is only from the resonant frequency the lc circuit lets through $\endgroup$ – Chris Bolig Sep 4 at 3:57
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    $\begingroup$ regarding the power, right now im a bit out of practice but I think that you may get the current in the second wire using ampere's law and faraday-lenz law. Then you can compute power $\endgroup$ – Javi Sep 4 at 4:37

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