PURPOSE: To demonstrate damped oscillations in an RLC circuit.

DESCRIPTION: Using the circuit below with a 500-Hertz square wave, damped oscillations are shown on the dual trace scope. The lower trace is the applied square wave and the upper trace shows the damped oscillations produced each time the square wave changes. The circuit can be adjusted to obtain either underdamped, overdamped, or critically damped oscillations by changing the capacitance or the resistance.

SUGGESTIONS: In the photograph above the horizontal scale is 250 microseconds per centimeter, the frequency of the square wave is 500 Hertz (period of 2 milliseconds), and the frequency of the damped oscillations is about 8000 Hertz (period of 125 microseconds). The capacitor is set to its maximum vlue and the resistor is set to about 20% of its maximum (20 kilohms).

REFERENCES: (PIRA unknown.) See Demonstration Reference File for further information regarding theory of damped electrical oscillations.

EQUIPMENT: Commercial RLC circuit in box with capacitor substitution box, oscillator, and dual trace scope.

SETUP TIME: 5 min.