Electric Circuits Lab
Series RL Circuits: Phase Angle, Phase Lead, and Inductors as Differentiators
I. Objectives:
After completing this lab experiment, you should be able to:
1. Understand the effect of frequency on inductive reactance.
2. Measure the impedance of an RL circuit.
3. Measure the phase angle and phase lead of an RL circuit using the oscilloscope.
4. Draw the impedance and voltage phasor diagrams.
5. Understand how an inductor differentiates current.
II. Parts List:
1. Resistors 100 Ω, 1 kΩ, 10 kΩ.
2. Inductors 1 µH, 100mH.
III. Procedures:
Part I :
1. Connect the following circuit.
Figure 1: RL Circuit
2. Connect one DMM across the resistor and one DMM across the inductor. 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 RL circuit, the same current will flow through the inductor and the resistor. Record the result in Table 1.
4. Calculate the inductive reactance using Ohm’s law. Record the result in Table 1.
5. Finally, calculate the inductive reactance using the inductive reactance equation. Record the result in Table 1.
Inductor L1 

Voltage across, R 
845.958 mV 
Voltage across, L 
533.246 mV 
Total Current, I 
0.846 mA 
Inductive Reactance, XL 
630.35 ohms 
Computed Reactance, XL 
628.32 omhs 
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 inductor. Record your measurements.
Frequency (in Hz) 
VR (measured) 
VL (measured) 
I =

XL =

XL = 2πfL (calculated) 
300 
982.58 mV 
185.81 mV 
0.9856 mA 
189.10 ohms 
188.50 ohms 
1k 
845.958 mV 
533.246 mV 
0.846 mA 
630.35 ohms 
628.32 ohms 
3k 
467.467 mV 
833.996 mV 
0.468 mA 
1.78 kΩ 
1.88kΩ 
5k 
302.425 mV 
953.161 mV 
0.302 mA 
3.15 kΩ 
3.14 kΩ 
7k 
221.027 mV 
975.265 mV 
0.221 mA 
4.41 kΩ 
4.40 kΩ 
9k 
173.593 mV 
984.811 mV 
0.174 mA 
5.66 kΩ 
5.66 kΩ 
11k 
142.743 mV 
989.751 mV 
0.143 mA 
6.92 kΩ 
6.91 kΩ 
13k 
121.133 mV 
992.626 mV 
0.121 mA 
8.20 kΩ 
8.17 kΩ 
15k 
105.174 mV 
994.442 mV 
0.105 mA 
9.47 kΩ 
9.43 kΩ 
Table 2: Calculated and measured values
7. Plot the graph for Frequency vs. VL.
(Use Word or Excel to create the plot)
Figure 2. Plot of Frequency vs. Inductor Voltage
Part II:
8. Build the circuit in Figure 2.
Figure 2: Series LR Circuit
9. Set the voltage source amplitude to 1.5 VP and frequency to 25 kHz, sine wave
10.