1. Plumber’s LCR Analogy Valve P1 P2 Rubber Diaphragm Flywheel
The “plumber’s analogy” of an LC circuit is a rubber diaphragm that has been stretched by pressure on the top (P1) side. When the valve starts the flow, the diaphragm forces water past the flywheel, which begins to spin. After the diaphragm has become flat, the momentum of the flywheel forces the diaphragm to be stretched in the other direction, and the cycle repeats. P3
Valve = Switch Rubber Diaphragm = Capacitor
Flywheel = Inductor Pressure = Potential Water Flow = Current

2. What is the best variable to plot for the LRC lab? ADMITTANCE
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What is the best variable to plot for the LRC lab? ADMITTANCE
Amplitude of I/Vext
w ->
The undriven system will oscillate at
Errata: in general, the driven resonance frequency
(see PS #2b to solve for it, it will be close)
L8 LRC circuit

4. Capacitor AC Circuits
The AC current through a capacitor leads the capacitor voltage by p/2 rad or The phasors for VC and IC are perpendicular, with the IC phasor ahead of the VC phasor.

5. C C circuit I V=q/C Vext Look for Purely capacitive circuit:
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C circuit C I
V=q/C
Vext
Look for
Purely capacitive circuit:
Current leads driving voltage (ICE)
Magnitude depends on frequency
dependent on w
L8 LRC circuit

6. C C circuit input I V=q/C Vext output Phasor diagram ICE Impedance, Z
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C circuit
input C I
V=q/C
Vext
output
Phasor diagram
ICE
Impedance, Z I
Vext
Admittance, 1/Z
L8 LRC circuit