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Re: [Phys-L] Ex: Re: RLC lab



That does sound right, doesn’t it? Let me try measuring the voltage aross the resistor instead, as a proxy for the current.

On Apr 18, 2022, at 4:16 PM, John Mallinckrodt <ajm@cpp.edu> wrote:

Maybe I’m misunderstanding something or maybe I’ve just been out of the classroom for too long, but shouldn’t basically all of the applied voltage appear across the coil at high frequencies?

On Apr 18, 2022, at 1:12 PM, Brian Whatcott <betwys1@sbcglobal.net> wrote:

 We might suppose that the large inductor is close-wrapped, so that the interwinding capacitance largely cancels the inductive reactance at say 1 kHz leaving 60 ohms contribution in a series circuit of 60 ohms, 188 ohms due to the capacitor at 1 kHz, and 100 ohms, a total of 348 ohms so that the coil contributes 60/348 of 5 volts = 0.9 volts of the volts drop.
On Monday, April 18, 2022, 02:28:29 PM CDT, Carl Mungan via Phys-l <phys-l@mail.phys-l.org> wrote:

I’m doing an RLC lab tomorrow. I’m using a coil with an inductance of about 0.9 H and a resistance of about 60 ohms (both measured using a handheld meter). I connect it in series to a capacitor of 1 microfarad and an additional resistor of 100 ohms. So resonance is around 180 Hz. I use a Pasco function generator with an amplitude of about 5 V.

Measuring the voltage across the coil does give a peak around there. At low frequencies, the voltage goes to zero, but on the high-frequency end the voltage does not go to zero but instead levels off at quite a high value (maybe 1 V or more).

What’s the primary reason the voltage stays so high across the coil at high frequencies? (And when I say high, I mean above a few hundred hertz, not super high.)

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Carl E. Mungan, Professor of Physics 410-293-6680 (O) -3729 (F)
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