1 Objectives

In this third lab session, as the Analog Discovery 2’s have been backordered and we will not be getting them to most students in a timely matter, we will be doing the lab using a simulation tool. This lab will introduce some basic AC circuit concepts using the CircuitJS simulator. The objectives are as follows:

Introduce the following simulators:

  • CircuitJS (Falstad Circuit Simulator)

Introduce the following concepts:

  • Impedance.
  • RMS, peak and peak-to-peak measurements of sine waves.
  • An AC voltage divider.
  • A series resistor-capacitor circuit as a variable voltage divider dependant on frequency.
  • A series resistor-inductor circuit as a variable voltage divider dependant on frequency.

1.1 Equipment Required

2 Procedures

2.1 Resistor Circuit (part 1)

  1. Learn to use the CircuitJS circuit simulator by following along with this video to create and simulate your first circuit as shown below:

    first AC circuit

    first AC circuit

    • Use this link (or the link in the upper right had corner of this webpage) to start a blank CircuitJS simulation.

  2. Use the tools in CircuitJS to measure the following for the circuit created in the video, set the AC source at 5V@200Hz connected to a 270Ω resistor, record all of the following measurements in the appropriate place on your results sheet:

    • VRMS - The RMS voltage across the resistor.
    • VMAX or VPEAK - The peak or max voltage across the resistor.
    • VMIN - The minumim voltage across the resistor.
    • VP2P - The peak-to-peak voltage across the resistor
    • IRMS - The RMS current through the resistor.

2.2 Resistor Circuit (part 2)

  1. Use the same CircuitJS circuit you created in part 1 to experiment with how the circuit is effected; first by frequency, then by voltage and finally by resistance.

    1. With the source voltage (VS) set to 5VPEAK and the resistor (R1) value set to 270Ω adjust the source frequency (fS) to 100Hz, 200Hz and 500Hz while measuring both the RMS voltage and RMS current for each frequency. Make sure to record your results in the appropriate place in the results sheet.

    2. With the source frequency (fS) set to 200Hz and the resistor (R1) value set to 270Ω adjust the source voltage (VS) to 1VPEAK, 2VPEAK and 5VPEAK while measuring both the RMS voltage and RMS current for each source voltage. Make sure to record your results in the appropriate place in the results sheet.

    3. With the source voltage (VS) set to 5VPEAK and the source frequency (fS) set to 200Hz adjust the value of the resistor (R1) to 120Ω, 270Ω and 560Ω while measuring both the RMS voltage and RMS current for each frequency. Make sure to record your results in the appropriate place in the results sheet.

2.3 Series Resistors

  1. To experiment with how the AC voltage and AC current in a circuit behave with 2 components in series we are first going to look at a resistor divider to see how the source frequency effects the circuit.

    1. Open this CircuitJS simulation as a template to complete the rest of the laboratory. The schematic diagram of this circuit is shown below:

      resistor divider circuit

      resistor divider circuit

    2. Watch this video that explains some more details about using the simulator.

    3. With the source voltage (VS) set to 5VPEAK and the source frequency (fS) set to 100Hz measure the RMS voltages across the source and both resistors. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    4. Adjust the source frequency (fS) to 1.0kHz and measure the RMS voltages across the source and both resistors again. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    5. Lastly adjust the source frequency (fS) to 10kHz and measure the RMS voltages across the source and both resistors again. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

2.4 Series RC (1uF)

  1. Replace the 220Ω resistor from the circuit used in the last section with a 1uF capacitor to demonstrate the effect frequency has on this new circuit.

    1. Modify the CircuitJS simulation from before so the 220Ω resistor is replaced with a 1uF capacitor to create the following circuit:

      RC divider circuit (1uF)

      RC divider circuit (1uF)

    2. With the source voltage (VS) set to 5VPEAK and the source frequency (fS) set to 100Hz measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuit’s RMS current. Make sure to record your results in the appropriate place in the results sheet.

    3. Adjust the source frequency (fS) to 338.6Hz and measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    4. Adjust the source frequency (fS) to 1.0kHz and measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    5. Lastly adjust the source frequency (fS) to 10kHz and measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

2.5 Series RC (100nF)

  1. Replace the 1uF capacitor from the circuit used in the last section with a smaller capacitance of 100nF to demonstrate the effect frequency has on this new circuit.

    1. Modify the CircuitJS simulation from before by changing the value of the capacitor from 1uF to 100nF to create the following circuit:

      RC divider circuit (100nF)

      RC divider circuit (100nF)

    2. With the source voltage (VS) set to 5VPEAK and the source frequency (fS) set to 100Hz measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuit’s RMS current. Make sure to record your results in the appropriate place in the results sheet.

    3. Adjust the source frequency (fS) to 1.0kHz and measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    4. Adjust the source frequency (fS) to 3.386kHz and measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    5. Lastly adjust the source frequency (fS) to 10kHz and measure the RMS voltages across the source, the resistor and the capacitor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

2.6 Series RL (10mH)

  1. Replace the 100nF capacitor from the circuit used in the last section with a 10mH inductor to demonstrate the effect frequency has on this new circuit.

    1. Modify the CircuitJS simulation from before so the 100nF capacitor is replaced with a 10mH inductor to create the following circuit:

      RL divider circuit (10mH)

      RL divider circuit (10mH)

    2. With the source voltage (VS) set to 5VPEAK and the source frequency (fS) set to 100Hz measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuit’s RMS current. Make sure to record your results in the appropriate place in the results sheet.

    3. Adjust the source frequency (fS) to 1.0kHz and measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    4. Adjust the source frequency (fS) to 7.480kHz and measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    5. Lastly adjust the source frequency (fS) to 10kHz and measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

2.7 Series RL (100mH)

  1. Replace the 10mH inductor from the circuit used in the last section with a larger inductance of 100mH to demonstrate the effect frequency has on this new circuit.

    1. Modify the CircuitJS simulation from before by changing the value of the inductor from the 10mH to 100mH to create the following circuit:

      RL divider circuit (100mH)

      RL divider circuit (100mH)

    2. With the source voltage (VS) set to 5VPEAK and the source frequency (fS) set to 100Hz measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuit’s RMS current. Make sure to record your results in the appropriate place in the results sheet.

    3. Adjust the source frequency (fS) to 748Hz and measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    4. Adjust the source frequency (fS) to 1.0kHz and measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

    5. Lastly adjust the source frequency (fS) to 10kHz and measure the RMS voltages across the source, the resistor and the inductor. Also measure the circuits RMS current. Make sure to record your results in the appropriate place in the results sheet.

2.8 Cleanup

Congratulations, you have completed the experimental part of the the laboratory. Before finishing, I’d suggest going through your results to check that you have completed everything and that your results make sense. If you find any issues, I’d suggest resolving or making a note of it now.

3 Results

The following is what you are expected to complete and submit for grading for Lab 3 before the deadline.

  1. The completed Lab 3 - Results sheet template provided at the beginning of this lab manual under Equipment required. This sheet should include the following:

    • Your name, student ID and CCID.
    • All of the required measurements from the lab procedures.
    • All of the required calculations as discussed below.
    • The required plots as discussed below.

The Lab 3 - Results sheet needs to be submitted to the Submit (Lab 3 - Results) link on eClass as a pdf document .

  1. Complete the online Quiz (Lab 3 - Post Lab) on eClass.

3.1 Calculations

For these calculation you only need to provide the answers in the space provided on your results sheet, you do not need to show your work.

  1. For the Resistor Circuit (part 2) calculate the resistance of each circuit by using the appropriate voltage and current measurements. Also calculate the period of a cycle for each of the frequencies used in this section.

  2. For the Series Resistors circuit calculate the simple sum of the RMS voltages across both of the resistors. Also calculate the resistance for each resistor: R1 and R2 for each frequency value using the appropriate voltage and current measurement.

  3. For the Series RC (1uF) and Series RC (100nF) circuits calculate the simple sum of the RMS voltages across the 2 series components; the resistor and capacitor (Note: this will not equal the supply voltage). Also use the appropriate voltage and current measurement to calculate the resistance of the resistor and reactance of the capacitor at each frequency. From the calculated reactance value also calculate the capacitance of the capacitor at each frequency.

  4. For the Series RL (10mH) and Series RL (100mH) circuits calculate the simple sum of the RMS voltages across the 2 series components; the resistor and inductor (Note: this will not equal the supply voltage). Also use the appropriate voltage and current measurement to calculate the resistance of the resistor and the reactance of the inductor at each frequency. From the calculated reactance value also calculate the inductance of the inductor at each frequency.

3.2 Plots

To create your plots you can use whichever software you would like (Excel, Matlab, etc), export your plot as an image and import it into your Lab 3 - Results sheet in the appropriate place.

Your plots should include:

  • A Plot title
  • Label your axes and show what unit of measure is used.
  • Include a marking for your datapoints.
  • Include a line between your datapoints in the same series.
  • Include a legend.
  • Make sure your scales are appropriate and visible.
  1. Impedance-Frequency Plot: For the 6 components used in the 5 different demonstration series circuits: 220Ω, 470Ω, 1uF, 100nF, 10mH and 100mH. Plot each components impedance vs. frequency on the same plot. Use a logarithmic scale for both the x-axis and y-axis.

3.3 Questions

Complete the online Quiz (Lab 3 - Post Lab) on eClass.