Week 3 Lab 2 Series RC Circuits Lab Report

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ECPI University, Virginia Beach *

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111

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Electrical Engineering

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Dec 6, 2023

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Electric Circuits Lab Instructor: Cameron Ruddy Series RC Circuits Student Name(s): Brandon Walker Click or tap here to enter text. Honor Pledge: I pledge to support the Honor System of ECPI. I will refrain from any form of academic dishonesty or deception, such as cheating or plagiarism. I am aware that as a member of the academic community, it is my responsibility to turn in all suspected violators of the honor code. I understand that any failure on my part to support the Honor System will be turned over to a Judicial Review Board for determination. I will report to the Judicial Review Board hearing if summoned. Date: 0/19/2023

Contents Abstract ....................................................................................................................................................... 3 I ntroduction ................................................................................................................................................ 3 Procedures ................................................................................................................................................... 3 Data Presentation & Analysis ....................................................................................................................... 4 Calculations ............................................................................................................................................. 4 Required Screenshots .............................................................................................................................. 4 Conclusion ................................................................................................................................................... 4 References ................................................................................................................................................... 5 2

Abstract The lab we are completing will help us better understand how to measure the impedance of a RC circuit. During the lab we will understand the effect of frequency on capacitive reactance while using a oscilloscope. The use of the oscilloscope will also help us measure phase angles, phase lag and better understand capacitor currents. I ntroduction We find that impedance of a rc circuit is opposition of flow in a a/c circuit with the formula Z=R+1/jwC. We find that phase angle represents the phase shift between voltage across the resistor and voltage across the capacitor it is calculated using 0=arctan(-1/wRC). We understand that phase lag is when the output voltage lags behind the input voltage using the calculation 0=arctan(-1/wRC). Capacitors are able to integrate current because they store electrical energy in a electric field between the plates with the equation Q=C*V. Procedures Part I: 1. Connect the following circuit. VS R1 1.0kΩ C1 0.1µF 1Vrms 1 kHz Figure 1: RC Circuit 3

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 = V R R 4. Calculate the capacitive reactance using Ohm’s law. Record the result in Table 2 . Capacitive Reactance, X C = V C I 5. Now, calculate the capacitive reactance value using the equation below. Record the result in Table 1 under Computed Reactance, X C . Capacitive Reactance, X C = 1 2 πfC 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. 7. Plot the graph for Frequency vs. V C . Part II: 8. Build the circuit shown in Figure 2 . 4

Figure 2: Series RC Circuit 9. Set the source voltage amplitude to 1.5 V p and frequency to 500 Hz. 10. Connect Channel A of the oscilloscope across the resistor and measure the peak voltage drop (V R ). Record the result in Table 3 . 11. Use Ohm’s law to calculate the peak current flowing through the resistor. Because it is a series circuit, the same current will flow through the capacitor. Record the result in Table 3. Total current I = V R R 12. Connect Channel B of the oscilloscope across the capacitor and measure the peak voltage drop (V C ). Record the value in Table 3 . 13. Calculate the capacitive reactance using Ohm’s law. Record the result in Table 3 . Capacitive Reactance X C = V C I 14. Now, calculate the total impedance (Z T ) value using the equation below. Record the result in Table 3 . Total Impedance (Z T ) = V S I 5

15. Calculate the phase angle between V R and V S using the formula below. Record the result in Table 3 . Also, record this value in Table 4 under Phase Angle calculated value. Phase angle, θ =− tan − 1 ( X C R ) Part III: Phase Angle and Phase Lag Measurement Phase Angle 16. Connect Channel A of the oscilloscope across the resistor and Channel B of the oscilloscope across the function generator and run the simulation. 17. The waveforms should look like the ones shown in Figure 4 . Figure 4: V S and V R waveforms 18. Obtain a stable display showing a couple of cycles for Channel B (which is showing V S ) and disable Channel A by setting it to 0. 19. Measure the time period (T) of the source voltage. Record the result in Table 4 . (Use the cursors to measure the period (on the scope it will show as T2-T1). Remember that the period is the time taken to complete one cycle). See Figure 5 . 6

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