Re: [Phys-L] RLC lab

[John Denker <jsd@av8n.com>]

On 4/18/22 12:28 PM, Carl Mungan via Phys-l wrote:

> What’s the primary reason the voltage stays so high across the coil
> at high frequencies?

Standard analysis: Start by getting the asymptotes:

Given: Series RCL, drive the stack with constant voltage,
measure voltage across the inductor.

At low frequency, the L is a dead short, the C is an
open circuit, and the R is a detail.
Measured V is small and falls off at 12 dB per octave.

  It won't really go to zero because of parasitic resistance
  within the coil, but it should get close.

At high frequency, the C is a dead short, the L is an
open circuit, and the R is a detail.
Measured V equals input V.

Asymptotes intersect at the nominal resonance frequency.

https://www.av8n.com/physics/img48/rlc-vl.png

Derivation for similar circuits is here:
  https://www.av8n.com/physics/rlc.htm

although this particular case is not detailed there.

==========================

> Pasco function generator

What's the output impedance of that?
If it's not small compared to 60 Ω it could mess you up.

If in doubt, measure *both* Vdrive and Vinductor.
Or do a separate experiment to ascertain the output impedance
and add that to the explicit 60 Ω component you installed.