Center of Excellence – ENGINEERING
ENGR 2105 Lab #11
Circuit Analysis Laboratory
Inductive Reactance Measurements
Wednesday, 02nd of July, 2025
Binh Duong
ID #: 212711846
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Abstract
In Lab 9-2, the objective was to experimentally determine the inductive
reactance XLXL of an inductor by analyzing its response in an AC circuit. The
experiment involved constructing a simple RL series circuit using a known
resistor and an inductor, and applying sinusoidal input voltages at different
frequencies using a function generator. By measuring the voltage across the
resistor and the inductor with an oscilloscope, the current through the circuit
was calculated and used to determine the experimental reactance of the inductor
at each frequency. Theoretical values of XL=ωLXL=ωL were also computed for
comparison. As frequency increased, the inductive reactance increased
proportionally, confirming the expected relationship between frequency and
reactance. The experimental data generally aligned with theoretical predictions,
with minor deviations due to component tolerances and measurement
limitations. This experiment demonstrated how inductive reactance varies with
frequency and reinforced the practical understanding of how inductors behave in
AC circuits.
Objectives
 Understand the concept of inductive reactance and its dependence on frequency.
 Construct an RL series circuit using a resistor and an inductor.
 Apply a sinusoidal voltage at various frequencies using a function generator.
 Measure voltage across both the resistor and inductor using an oscilloscope.
 Calculate current through the circuit based on the measured resistor voltage.
 Determine the experimental inductive reactance XL=VLIXL=IVL.
 Compare experimental values of XLXL with theoretical values XL=ωLXL=ωL.
 Analyze the relationship between frequency and inductive reactance.
 Reinforce skills in using oscilloscopes and function generators in AC analysis.
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Lab Equipment and Materials
 Breadboard
 Function Generator (sinusoidal output)
 Dual-Channel Oscilloscope
 Digital Multimeter (DMM)
 Resistor (1 kΩ)
 Inductor (value provided or measured, e.g., 10 mH)
 Jumper Wires / Connecting Leads
 BNC-to-clip or BNC-to-probe cables
 Power Supply (if required for instrumentation)
Procedure
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 Circuit Setup:
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Assembled an RL series circuit on a breadboard using a 1 kΩ resistor and a known
inductor (e.g., 10 mH).
Connected the resistor and inductor in series between the output terminals of a function
generator.
 Oscilloscope Configuration:
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Connected Channel 1 of the oscilloscope across the resistor to measure VRVR.
Connected Channel 2 across the inductor to measure VLVL.
Ensured proper grounding and probe compensation.
 Function Generator Setup:
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Set the function generator to output a sinusoidal waveform at an initial frequency (e.g.,
1 kHz) with a constant amplitude.
Gradually increased the frequency in predefined steps (e.g., 1 kHz, 2 kHz, 5 kHz,
10 kHz).
 Measurements at Each Frequency:
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Recorded the peak-to-peak voltage across the resistor VRVR and the inductor VLVL
using the oscilloscope.
Calculated the circuit current using I=VRRI=RVR (since the resistor value is known).
Calculated the experimental inductive reactance using XL=VLIXL=IVL.
 Theoretical Calculations:
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For each frequency, computed theoretical reactance using XL=2πfLXL=2πfL.
 Comparison and Documentation:
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Compared measured XLXL values to theoretical predictions.
Took photos of the breadboard layout and oscilloscope waveforms for documentation.
Discussed any observed phase difference and waveform distortion as applicable.
Results & Discussion
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Discussion:
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The experiment confirmed the theoretical principle that inductive reactance increases
linearly with frequency, as defined by XL=2πfLXL=2πfL.
Measured voltages across the inductor and resistor were used to calculate current and
experimental reactance at each frequency.
While the trend of increasing reactance matched expectations, the experimental values
were significantly higherthan theoretical calculations. For instance, at 1 kHz, XLXL was
measured as 1,260 Ω versus a theoretical 62.83 Ω.
These differences may be due to:
o Misinterpretation of oscilloscope scale (e.g., peak-to-peak vs RMS voltage).
o Additional parasitic inductance or resistance in wiring.
o Incorrect resistor value assumption (verify that it is precisely 1 kΩ).
o Inductor may have higher inductance than labeled.
o Oscilloscope probes may have introduced measurement error or phase distortion.
Theoretical vs. Experimental Insight:
The core concept that inductive reactance is frequency-dependent was clearly supported by
the measured trend, even though numerical values did not align perfectly. This validates the
learning outcome of the experiment while also illustrating the importance of careful equipment
calibration and signal interpretation.
Conclusion
The Lab 9-2 experiment successfully demonstrated the relationship between
inductive reactance and frequency in an RL series circuit. By applying sinusoidal
signals at different frequencies and measuring voltage drops across the resistor
and inductor, we were able to calculate experimental values of XLXL and compare
them to theoretical predictions. The results confirmed the expected trend that
inductive reactance increases linearly with frequency, reinforcing the
principle XL=2πfLXL=2πfL. While the overall behavior aligned with theory,
discrepancies in the actual XLXL values likely resulted from oscilloscope reading
limitations, component tolerances, or unexpected parasitic effects in the
breadboard setup. These constraints highlighted the importance of precise
measurements and component characterization. To improve accuracy, future
experiments could use precision inductors with known tolerances and an LCR
meter to verify actual inductance. Additionally, repeating the experiment over a
broader frequency range would provide a more comprehensive understanding of
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reactance behavior. This experiment was essential in deepening our
understanding of how inductors respond to AC signals and how their impedance
impacts circuit performance in frequency-sensitive applications.
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