ANADOLU UNIVERSITY
DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING
EEM 102 INTRODUCTION TO ELECTRICAL ENGINEERING
EXPERIMENT 7:
RC CIRCUITS
Prepared by Prof.Dr. Atila BARKANA
OBJECTIVE:
To examine the response of RC circuits to frequency changes.
PRELIMINARY WORK:
Solve the circuits in A, B, and C using the nominal values of capacitors and resistors. Prepare
copies of Table 1, Table 2 and Table 3, and fill them out. Plot Hdb versus w on the same graph
paper for each of the circuits. You can use the second graph paper on the last page.
AC CIRCUITS:
Since the impedance of L and C elements change as frequency changes, the behavior of the ac
circuits changes as well. This behavior will be examined in this experiment and the frequency
response of the circuits will be drawn on a semi-logarithmic graph paper. In order to observe
the behavior of the circuits, the ratio of the output voltage to the input voltage is used.
A. RC Circuit
1. Setup the circuit below.
2. Set the frequency of the function generator to 10 Hz.
3. Select sinusoidal signal and adjust amplitude of the signal so that the first voltmeter V1
reads Vi= 1.00 Vrms.
4. Read the output voltage Vo from the second voltmeter V2.
5. Change the frequency as you see in Table 1 and fill out the table. The output of the function
generator may change as you change the frequency. So, adjust the amplitude, if necessary, of
the signal to 1.00 Vrms at each frequency change.
NOTE: As you change the frequency, the ratio of the output voltage to the input voltage is
calculated to obtain how much of the input voltage is transferred to the output at each
frequency. Then this ratio is expressed in decibels (db) using the formula below.
Hdb = 20 log
6. Calculate HdB for each frequency and plot HdB versus w on the semi-logarithmic paper
given.
BANDWIDTH:
After plotting HdB, you go down 3 dB from its maximum value, and the distance between the
points where this line crosses the HdB curve is the bandwidth. These frequencies are called the
half-power frequencies.
RMS VOLTAGE:
Ac voltages and also currents are generally given by their effective values. The effective
values are also called root-mean-square (rms) values. If an ac voltage is expressed as
V(t) = Vm cos (wt+α)
Then its rms value is given as
Vrms = Veff =
Vm
2
Vrms is the value the AC voltmeters measure.
B. CR Circuit
1. Setup the circuit below.
2. Repeat A.2 to A.6, filling out Table 2 and plotting HdB versus w on the same graph paper.
C. A more complex circuit
1. Setup the circuit below.
2. Repeat A.2 to A.6, filling out Table 3 and plotting HdB versus w on the same graph paper.
Use a different color pencil.
Name: …………………………..
No :…………………………......
Table No:……………………….
EXPERIMENT 7
RC CIRCUITS
REPORT
A: RC Circuit:
Table 1 : Output of the RC Circuit.
Frequency f (Hz)
10
20
40
100
200
400
1000
2000
4000
10000
20000
40000
Frequency w
(rad/s)
63
126
251
628
1257
2513
6283
12566
25133
62832
125664
251328
Vout(rms)
HdB
1. Plot Hdb versus w on the graph paper given. What can you say about this curve?
.......................................................................................................................................................
.......................................................................................................................................................
.......................................................................................................................................................
2. Draw the horizontal line 3-dB below the maximum. What is the half-power frequency?
.......................................................................................................................................................
3. What are the slopes of the curve?
Below 5000 rad/s: ......................... dB/decade
......................... dB/octave
Above 100 Krad/s: ......................... dB/decade
......................... dB/octave
B. CR Circuit:
Table 2 : Output of the CR circuit.
Frequency f (Hz)
10
20
40
100
200
400
1000
2000
4000
10000
20000
40000
Frequency w
(rad/s)
63
126
251
628
1257
2513
6283
12566
25133
62832
125664
251328
Vout(rms)
HdB
1. Plot Hdb versus w on the same graph paper. What can you say about this curve?
.......................................................................................................................................................
.......................................................................................................................................................
.......................................................................................................................................................
2. What is the half-power frequency? ..........................................................................................
3. What are the slopes of the curve?
Below 100 rad/s: ......................... dB/decade
......................... dB/octave
Above 3000 Krad/s: ......................... dB/decade
......................... dB/octave
C. A more complex circuit:
Table 3 : Output of the complex circuit.
Frequency f (Hz)
10
20
40
100
200
400
1000
2000
4000
10000
20000
40000
Frequency w
(rad/s)
63
126
251
628
1257
2513
6283
12566
25133
62832
125664
251328
Vout(rms)
HdB
1. Plot Hdb versus w on the same graph paper. What can you say about this curve?
.......................................................................................................................................................
.......................................................................................................................................................
.......................................................................................................................................................
2. What are the half-power frequencies?
..........................................................................................
3. What is the bandwidth? ............................................................................................................
Date:
Table No:
Name:
No:
Pre-Lab
Grades
Report
Performance
Total