Week 3 Lab 2 Series RC Circuits Lab Report

docx

School

ECPI University, Virginia Beach *

*We aren’t endorsed by this school

Course

111

Subject

Electrical Engineering

Date

Dec 6, 2023

Type

docx

Pages

22

Report

Uploaded by MinisterPower10030

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
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
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
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
Figure 5: Measuring time period (T) 20. Now set the oscilloscope to view both the channels. 21. Adjust the amplitude of the signals using Channel A and Channel B V/Div scale until both channels appear to have the same amplitude as seen on the scope face. (as close as possible) 22. Spread the signals horizontally using the Timebase (Sec/Div) control until both signals are just visible across the screen as shown below. 23. Measure the time duration between the two signals (∆t) and record the result in Table 4 . (Use cursors as shown below in Figure 6 ) Figure 6: Measuring the time difference 7
24. Calculate the phase angle using the formula below and record the result in Table 4 . Phase angle, θ = (∆t/T) * 360° Phase Lag 25. Connect your circuit as shown in Figure 7 . When the output of an RC circuit is taken across the capacitor, the circuit is called an RC lag circuit. The output voltage in an RC lag circuit will lag the input voltage. Figure 7: RC Lag Circuit 26. Calculate the phase lag using the equation below. Notice the similarity to the equation for the phase angle. The phase lag angle and phase angle of an RC circuit are complementary angles. (Their sum is 90°.) Use R and X C values from Table 3 . Phase Lag, ϕ = tan 1 ( R X C ) 27. Measure the time period (T) of the source voltage (as in Step 19). Record this value in Table 4 . 28. Now set the oscilloscope to view both the channels. 8
29. Adjust the amplitude of the signals using Channel A and Channel B V/Div scale until both channels appear to have the same amplitude as seen on the scope face. (as close as possible) 30. Spread the signals horizontally using the Timebase (Sec/Div) control until both signals are just visible across the screen as shown in Figure 6 . 31. Measure the time duration between the two signals (∆t) and record the result in Table 4 above. 32. Calculate the phase lag using the formula below and record the result in Table 4 . Phase lag, = (∆t/T) * 360° 33. Plot the Voltage and Impedance Phasor Diagrams. Clearly indicate the phase angle and the phase lag. Measure the peak voltages for V R and V C with the oscilloscope. Part IV: The Capacitor Integrates Current 34. Construct the following RC circuit in Multisim. Set the clock voltage source to 10 kHz, 10V, 50% duty cycle. Figure 9. Integrator Circuit 35. Connect Channel A across the resistor and Channel B across the capacitor. (Note: change one or both trace colors to better observe the two signals) 9
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
Figure 9a. Integrator Circuit with Oscilloscope Connections 36. Run the simulation. Your signals should look like the example in Figure 9b . Figure 9b: Capacitor as an integrator waveforms 10
37. Channel A will show the voltage across the resistor. This signal can be used to find the circuit current using Ohm’s law. 38. Channel B shows the voltage across the capacitor. Show that this signal satisfies the following equation. We will do this in intervals in the following steps. i = C dv dt v ( t ) = 1 C t i ( τ ) v ( t ) = 1 C t i ( τ ) = 1 C 0 t i ( τ ) + 1 C 0 i ( τ ) v ( 0 ) = 1 C 0 i ( τ ) v ( t ) = 1 C t i ( τ ) = 1 C 0 t i ( τ ) + v ( 0 ) 39. Refer to Figure 10 to answer the following questions. 11
Figure 10: Integrator values, 0 to 50 µs a. The signal has a period of 100 µs. Write the equation for the circuit current on the interval 0 to 50 µs. On the interval of 0 to 50 µs, v R (t) is constant so the current will be constant as well. i ( t ) = v R ( t ) R b. Write the equation for the voltage across the capacitor by solving the integral. You will need to read the value v C (0) from Figure 10 . 12
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
v ( t ) = 1 C 0 50 µs i ( x ) dx + v ( 0 ) c. Confirm your equation by predicting the value of v C (50 µs). d. Read the value of v C (50 µs) from Figure 10 . 40. Refer to Figure 11 to answer the following questions. Figure 11: Integrator values, 50 to 100 µs a. The signal has a period of 100 µs. Write the equation for the circuit current on the interval 50 µs to 100 µs. On the interval of 50 to 100 µs, v R (t) is constant so the current will be constant as well. 13
i ( t ) = v R ( t ) R b. Write the equation for the voltage across the capacitor by solving the integral. You will need to read the value v C (50) from Figure 11 . v ( t ) = 1 C 50 µs t i ( τ ) + v ( 50 µs ) c. Confirm your equation by predicting the value of v C (100 µs). d. Read the value of v C (100 µs) from Figure 11 . Data Presentation & Analysis Table 1: Calculated and measured values 14 Capacitor C 1 Voltage across, R 533.245mV Voltage across, C 845.958mV Total Current, I 0.533mA Capacitive Reactance, X C 1.587 ohm Computed Reactance, X C 1.5925 ohm
Table 2: Calculated and measured values Plot 1. Frequency vs. Voltage, V C 15 Frequency (in Hz) V R (measured) V C (measured) I = V R R (calculated) X C = V C I (calculated) X C = 1 ( 2 πfC ) (calculated) 300 185.809mV 982.579mV 186mA 5.284 ohm 530.5 ohm 1k 533.245mV 845.958mV 533mA 1.588 ohm 1591.55 ohm 3k 883.997mV 467.468mV 884mA 0.529 ohm 530.52 ohm 5k 953.162mV 302.426mV 953mA 0.317 ohm 318.31 ohm 7k 975.266mV 221.028mV 975mA 0.277 ohm 227.51 ohm 9k 984.812mV 173.593mV 985mA 0.176 ohm 176.71 ohm 11k 989.752mV 142.743mV 990mA 0.144 ohm 144.6 ohm 13k 992.627mV 121.134mV 993mA 0.122 ohm 122.1 ohm 15k 994.443mV 105.175mV 994mA 0.106 ohm 212.13 ohm Frequency (in Hz) V R (measured) V C (measured) 300 185.809mV 982.579mV 1k 533.245mV 845.958mV 3k 883.997mV 467.468mV 5k 953.162mV 302.426mV 7k 975.266mV 221.028mV 984.812mV 173.593mV 11k 989.752mV 142.743mV 13k 992.627mV 121.134mV 15k 994.443mV 105.175mV V R I V C X C Z T Ө 312.957 mV 45.99mA 1.460V 31.748 ohm 23.08 ohm 77.81
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
Table 3: Calculated and measured values Table 4: Phase angle and phase lag measurements 70 75 80 85 90 95 Chart Title Measured Angle Period (T) Calculated Angle Period (T) Plot 2(a) Impedance Phasor Plot 2(b) Voltage Phasor Calculations Part I step 3: I =0.533mA Part I step 4: X C =1.587 ohm Part I step 5: Xc =1.5925 ohm Part II step 11: I =45.99mA Part II step 13: X C =31.748 ohm 16 Type of Angle Measured Period (T) Time difference (∆t) Measured Angle Calculated Angle Phase angle θ 2.000 ms 432.812uS 77.81 77.81 Phase Lag Φ 2.000ms 432.812uS 77.81 89.9
Part II step 14: Z T =23.08 ohm Part II step 15: θ = ¿ 77.81 deg Part III step 24: θ = ¿ 77.81 deg Part III step 26: = ¿ 89.9 Part III step 32: = ¿ 77.81 Part IV step 39 a: i(t) =i(t)=1.992v/3000 ohm=664uA Part IV step 39 b: v c (t) = Vc ( t )= ωCI 0sin( ωt )−7.425×10−3 Part IV step 39 c: v c (50 µs) = Vc (50 μs )=-7.425×10−3V Part IV step 39 d: v c (50 µs) =7.425 Part IV step 40 a: i(t) = i (100 μs )=1.992V/3000=0.000664A=664 μ A Part IV step 40 b: v C (t) = vC ( t )= C 1(−664.3×10−6×( t −50×10−6))−7.424×10−3 Part IV step 40 c: v c (100 µs) = vC (100 μ s)=5.6×10−61(−664.3×10−6×(100×10−6−50×10−6)) −7.424×10−3 Part IV step 40 d: v c (100 µs) =7.457 Required Screenshots Figure 12: Screenshot of Waveforms for Part 2 Step 10 17
Figure 13: Screenshot of Waveforms for Part 2 Step 12 Figure 14: Screenshot of Waveforms for Part 3 Step 19 18
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
Figure 15: Screenshot of Waveforms for Part 3 Step 23 Figure 16: Screenshot of Waveforms for Part 3 Step 27 19
Figure 17: Screenshot of Waveforms for Part 3 Step 31 Figure 18: Screenshot of Waveforms for Part 3 Step 33 20
Conclusion Yes my measured and calculated capacitive reactance values agreed. As frequency increases the overall capacitive reactance decreases. My measured and calculated phase angle did not perfectly agree but are very close. In a RC circuit we find the voltage leading due to current lagging behind voltage. We find the phase angle decreases as frequency increases and phase angle increases as frequency decreases. My calculated and measured phase lag did not perfectly agree but are close. In the circuit we find the capacitor voltage lags behind the source voltage. Both phase angle and lag show the differences between the waves but lag is specific for one wave lagging behind the other while phase angle is the angular difference between the waves. As frequency increases the phase lag decreases and while frequency decreases the phase lag increases. 21
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help
References Floyd, T. L., & Buchla, D. M. (2019). Principles of Electric Circuits (10th Edition). Pearson Education (US). https://bookshelf.vitalsource.com/books/9780134880068 22
Your preview ends here
Eager to read complete document? Join bartleby learn and gain access to the full version
  • Access to all documents
  • Unlimited textbook solutions
  • 24/7 expert homework help