Showing the Effect of Frequency

Author: N.H. Crowhurst

Because the fluctuation of charge on a capacitor is something that takes time, the division of audio voltage drops between a capacitor and resistor in series will differ according to the applied frequency.

Oscilloscope Patterns

At a high frequency, a charge on the capacitor does not have time to change very much, and most of the voltage fluctuation appears across the resistor. At a low frequency, the charge on the capacitor has plenty of time to change, and can do so with a comparatively small current flowing through the resistor. Consequently, most of the voltage fluctuation appears across the capacitor. At an intermediate frequency the two voltages are about equal. Both of them are sine waves and they are "spaced" apart in time by a phase difference of 90°.