TOPIC:

ID Code: K7-45
Purpose: Demonstrate use of a series RL circuit as a low-pass filter and a series RC circuit as a high-pass filter.
Description: The circuits above have been mounted on a plastic base for use with an overhead projector. Low-pass filter with cutoff frequency f=R/L: The signal is input to the series RL circuit and the output is taken across the resistor. High-pass filter with cutoff frequency f=1/RC: The signal is input into the series RC circuit and the output is taken across the resistor. Values of circuit components are shown on the projectual. In each case the input signal is input into the upper trace of the scope and the filtered signal into the lower trace. Complex waves can also be input to see how removal of some harmonics affects the wave shape. In this demonstration the experimental crossover frequency is aboout 5 kHz, so the biggest change in the amplitude of the signal is between 1 kHz and 10 kHz. In the sequences of photographs above the effect of the low pass filter (first sequence) and the high pass filter (second sequence) are shown at 1 kHz and 10 kHz respectively.
Availability: Available