Swept RLC Circuit (5L20.11)

Description:

A RLC circuit is driven by a function generator and an oscilloscope displays the voltage across all four components of the circuit simultaneously. The frequency can be swept from below resonance (capacitive) to above resonance (inductive).

Procedure or Operation Notes:

The resonant frequency of a RLC circuit is dependant on the inductor and capacitor values. For a 10 Henry inductor and a 2,500 pF capacitor, the resonant frequency is 1007 Hz. While the inductance is very accurate (+/- 0.1%), the capacitor has a tolerance of +/- 20%. That means that the actual resonant frequency can be anywhere between 919 Hz and 1125 Hz.

Channel 1 (Yellow): Source (the Pasco function generator).
Channel 2 (Blue): 0 to 1 kΩ potentiometer.
Channel 3 (Magenta): 10 Henry inductor.
Channel 4 (Green): 2,500 pF capacitor.

When powered on, the Pasco function generators default to 1,000 Hz which is close to the resonant frequency of this circuit. Note that the voltage across the resistor is slightly lagging the voltage across the source, and that the inductor voltage is slightly higher than the capacitor voltage.

At 500 Hz, the circuit is capacitive:

At 1,500 Hz, the circuit is inductive:

By slowly adjusting the frequency on the function generator, we find that the actual resonant frequency of this circuit is approximately 951 Hz. Note that the resistor and source are in phase, and both the inductor and capacitor voltages are (approximately) equal.