Low-pass Filter and Corner Frequency

Lab 10 Low Pass and High Pass Filters

Objective
To study the behavior of RC and RL circuits when they are connected to AC power supply.

Material
Function generator, resistor, capacitor, inductor, wires, breadboard, oscilloscope

Procedure
RC Low Pass Filter We use a 10KΩ resistor and a 0.01μF capacitor in a series and prepare a function generator and a oscilloscope. Next, we measure the each voltage by changing the frequency (Start from 10, 20,30,50,70Hz). The measurement repeats for higher powers of ten, from the 100s to the high 10,000s.
We make a graph of Vc vs omega and Extend straight lines from the two regions to establish the corner frequency. Last, we compare it with predicted corner frequency.Repeat this experiment with a second capacitor.

RL High Pass Filter We use a 1KΩ resistor and a 25.0mH inductor in a series and prepare a function generator and a oscilloscope. Next, we measure the each voltage by changing the frequency (Start from 10, 20,30,50,70Hz) The measurement repeats for higher powers of ten, from the 100s to the high 10,000s.
In this case we find that it allows through high frequency signals but attenuates low frequency signals.We make a graph of Vc vs omega and extend straight lines from the two regions to establish the corner frequency. By using the corner frequency, we measure the inductance.

Data

f(Hz)
VC1
VC2
VL
10
8.8
8.8
3.0
20
10.0
10.0
3.0
30
10.3
10.4
3.4
50
10.4
10.6
3.5
70
10.5
10.6
3.6
100
10.5
10.5
3.6
200
10.4
10.2
4.0
300
10.4
9.8
4.2
500
10.0
8.6
5.0
700
9.6
7.4
6.0
1000
8.8
6.2
7.0
2000
6.4
3.8
9.2
3000
4.8
2.8
9.8
5000
3.2
1.8
10.4
7000
2.4
1.2
10.6
10000
1.8
1.0
10.8
20000
1.0
0.6
10.8
30000
0.8
0.4
11.0
50000
0.6
0.4
10.8
70000
0.6
0.4
10.8

For RC circuit:
R = 10 ± 5% kΩ
C1 = 0.01 ± 20% μF
C2 = 47 ± 20% μF

For RL circuit:
R = 100 ± 5% Ω
L = 25mH

Analysis for deriving C and L values