Description: The point of this demo is to show that an LCR (inductor-capacitor-resistor) circuit is a damped harmonic oscillator – when you give it a kick it oscillates for a while at the frequency omega=2*pi*f=(LC)^-1/2 but the oscillations die out due to dissipation in the resistor. In this demo, the resistance of the coil provides the R – there is no separate resistor, and the square wave provides periodic kicks. With each kick, the damped oscillations can be heard as a distinct note, and as the frequency is varied (by sliding the iron core in and out to change L) the note changes.