Course Title:
Electrical Engineering Fundamentals
Lab II
Academic Year: 2025/2026
Student ID:
Student name:
Course Code:
ECE 104
Semester:
Spring
24-101484
Malak Mohammed Fathy
*Don’t forget to hand in the report to the TA by the end of the lab session*
LAB MANUAL: Lab 2
RC Wave Shapes
Objectives
•
When you have completed this exercise, you will be able to demonstrate the effects of time
constants on RC circuit by using square waves as the applied ac waveforms. You will verify
your results with a universal time constant chart.
Procedure
1. If necessary, clear the AC 1 FUNDAMENTALS circuit board of all two-post connectors
and any other connections
2. Locate the RC/RL WAVE SHAPES circuit block, and connect the circuit shown. Adjust
VGEN for an 8 Vpk-pk, 100 Hz square wave. Use the oscilloscope to adjust the
frequency and amplitude
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3. The circuit shown is a simple RC circuit with a square wave input. As determined by R1 and
C1, the time constant (τ) of the circuit is: τ = R x C
4. Display the capacitor voltage (VC1) on the oscilloscope. Set the time base control to 1 ms/
div. Each major division along the horizontal axis should be equal to one time constant of the
circuit (1 ms). Adjust the oscilloscope controls so that the display resembles the one shown,
by selecting the proper trigger slope.
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5. If each major division along the horizontal axis equals one time constant, how many time
constants are required for the capacitor to fully charge?
a. 1
b. 3
c. 5
6. Using the oscilloscope, measure VC1 after C1 has charged for two time constants (2 ms) ,set
the probe to 10X.
VC1 =
V
7. Adjust the oscilloscope controls so that the display resembles the one shown below. The
oscilloscope display shows the discharge curve of the capacitor voltage (VC1). You may
have to select the proper trigger slope.
8. Measure VC1 after C1 has discharged for two time constants (2 ms) set the probe to 10X.
VC1 =
V
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9. Place CM switch 4 in the ON position to increase the value of R1 from 100 kΩ to 1M. This
change causes the period of the 100 Hz square wave to become too short to allow the
capacitor to charge and discharge fully. Connect the oscilloscope across C1, and toggle CM 4
off and on. What type of waveform results when CM 4 is activated?
a. square wave
b. sawtooth wave
c. sine wave
10. Locate the RC/RL WAVE SHAPES circuit block, and connect the circuit shown. The
voltage across R2 represents the circuit current.
11. Connect the oscilloscope probes as shown. Synchronize the oscilloscope on the positive edge
of VGEN (SLOPE set to positive, SOURCE set to CH 1). Display the voltage across R2
(VR2) on the lower half of the oscilloscope screen. NOTE: VR2 represents the circuit
current.
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12. Judging from the waveforms displayed, would you say current flow is maximum at the
beginning or at the end of the charge and discharge times?
a. beginning
b. end
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Review Questions
1. A capacitor in an RC circuit is considered to be fully charged after
a. 4 time constants.
b. 1 time constant.
c. 3 time constants.
d. 5 time constants.
2. A series RC circuit consisting of a 4.7 mF capacitor and a 4.7 kΩ resistor has a time constant
value of
a. 22.1 ms.
b. 45.3 s.
c. 221 ms.
d. 4.53 s.
3. The circuit current in an RC circuit is
a. maximum at the beginning of charging time.
b. minimum at the beginning of charging time.
c. maximum at the end of charging time.
d. minimum at the beginning of discharging time.
4. An RC circuit has an applied square wave with a period that is too short to allow the capacitor to
fully charge and discharge. The capacitor voltage produces a
a. square wave.
b. sine wave.
c. sawtooth wave.
d. cosine wave.
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