Electric Circuits Lab
Series RC Circuits: Phase Angle, Phase Lag, and Capacitors as Integrators
After completing this lab experiment using, you should be able to:
1. Understand the effect of frequency on capacitive reactance.
2. Measure the impedance of an RC circuit.
3. Measure the phase angle and phase lag of an RC circuit using the oscilloscope.
4. Draw the impedance and voltage phasor diagrams.
5. Understand how a capacitor integrates current.
II. Parts List:
1. Resistor 100 Ω, 1 kΩ, 6.8 kΩ
2. Capacitors 0.1 µF, 0.01 µF
1. Connect the following circuit.
Figure 1: RC Circuit
2. Connect one DMM across the resistor and one DMM across the capacitor. Set both DMMs to read AC voltage. Measure the voltage drop across each component. Record the result in Table 1.
3. Use Ohm’s law to calculate the current flowing through the resistor. Since the circuit in Figure 1 is a series RC circuit, the same current will flow through the capacitor and the resistor. Record the result in Table 1.
Total current, I =
4. Calculate the capacitive reactance using Ohm’s law. Record the result in Table 2.
Capacitive Reactance, XC =
5. Now, calculate the capacitive reactance value using the equation below. Record the result in Table 1 under Computed Reactance, XC.
Voltage across, R
Voltage across, C
Total Current, I
Capacitive Reactance, XC
Computed Reactance, XC
Table 1: Calculated and measured values
6. Adjust the function generator frequency following the steps in Table 2. Use the DMM to measure the voltage across the resistor and the capacitor. Record your measurements below.
Frequency (in Hz)
Table 2: Calculated and measured values
7. Plot the graph for Frequency vs. VC.
(Use Excel or Word to Create the Plot)
Plot 1: Frequency vs. VC
8. Build the circuit shown in Figure 2.
Figure 2: Series RC Circuit
9. Set the source voltage amplitude to 1.5 Vp and frequency to 500 Hz.
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