5L20.10 Damped Oscillations in a RLC Circuit and/or Phase Relations in Resonance

PURPOSE: To demonstrate RLC Circuits - AC

DESCRIPTION: In the same vein, it's possible to show (on an oscilloscope) damped oscillations in an RLC circuit, all the way from underdamped (ringing), to critically damped, to overdamped. With large inductors and capacitors, the oscillations can be made very slow. The effect is quite enchanting.

SETUP TIME: Medium

COMPONENT LIST:

    


  1.  Oscilloscope		??(Advanced lab?)


  2.  RLC circuit		(??)

SUGGESTIONS: For more advanced classes, it is possible to show phase relations in resonance. A dedicated device, built by Howey and Prosser, uses low-harmonic-distortion coils to monitor current and voltage in appropriate legs of the circuit, and ddisplay proportional signals on oscilloscopes. With dual-channel capability, one can see the current signal lagging the voltage when inductance dominates, then creeping up on the voltage as inductance (in an accompanying coil) is reduced; simultaneously the amplitude of the current increases as resonance is neared; right on resonance the current and voltage curves have their maximum amplitudes and lie exactly on top of each other, and a light bulb burns at its brightest. The extent to which this device reproduces the graphs in the electrical engineering textbooks is amazing.

REFERENCES: 2122 9.5, 9.55 ; PIRA 5L20.10

OTHER NOTES: