In a series LC circuit, resonance occurs when the Inductive Reactance (XL) is equal to the Capacitive Reactance (XC). Because XC and XL are 180 degrees out of phase the combined impedance is equal to zero. This is the point where the waveform encounters its least resistance and it will tend to oscillate at this frequency. We can calculate the values at resonance from the experiment to verify this theory.
The most obvious effect of changing the resistor value is to reduce the current flow at resonance. The current flow when R=0 ohms was .92ma. However, when the resistance was increased to 1500 ohms, the resonance current was reduced to .57ma. The current at 16HZ and 1600HZ remained nearly constant at R=0 ohms and R=1500 ohms. This is due to the capacitive reactance rising at 16HZ and the inductive reactance rising at 1600 HZ to about 10000 ohms. The increased reactance of the capacitor and inductor at these frequencies diminished the effect of the resistor.
Another effect was to alter the shape of the curve as the frequency varies from 16 to 1600 HZ. When R=0 ohms, the higher peak at resonance resulted in a sharper rate of increase and a more defined peak. When R=1500 ohms, the curve was more flattened and had a less well defined peak.
Damping is a term that describes the loss of energy in a circuit, thus causing the decay in amplitud ...