Performance-Based Assessments for AC Circuit Competencies

Use a sine-wave function generator for the AC voltage source. Specify standard resistor and capacitor values.

I recommend setting the function generator output for 1 volt, to make it easier for students to measure the point of “cutoff”. You may set it at some other value, though, if you so choose (or let students set the value themselves when they test the circuit!).

I also recommend having students use an oscilloscope to measure AC voltage in a circuit such as this, because some digital multimeters have difficulty accurately measuring AC voltage much beyond line frequency range. I find it particularly helpful to set the oscilloscope to the “X-Y” mode so that it draws a thin line on the screen rather than sweeps across the screen to show an actual waveform. This makes it easier to measure peak-to-peak voltage.

An extension of this exercise is to incorporate troubleshooting questions. Whether using this exercise as a performance assessment or simply as a concept-building lab, you might want to follow up your students’ results by asking them to predict the consequences of certain circuit faults.

Use a sine-wave function generator for the AC voltage source. Specify standard resistor and capacitor values.

I recommend setting the function generator output for 1 volt, to make it easier for students to measure the point of “cutoff”. You may set it at some other value, though, if you so choose (or let students set the value themselves when they test the circuit!).

I also recommend having students use an oscilloscope to measure AC voltage in a circuit such as this, because some digital multimeters have difficulty accurately measuring AC voltage much beyond line frequency range. I find it particularly helpful to set the oscilloscope to the “X-Y” mode so that it draws a thin line on the screen rather than sweeps across the screen to show an actual waveform. This makes it easier to measure peak-to-peak voltage.

An extension of this exercise is to incorporate troubleshooting questions. Whether using this exercise as a performance assessment or simply as a concept-building lab, you might want to follow up your students’ results by asking them to predict the consequences of certain circuit faults.

Use a sine-wave function generator for the AC voltage source. Specify components giving a notch frequency within the audio range:

I have had good success using the following values:

R₁ = 10 kΩ

R₂ = 10 kΩ

R₃ = 5 kΩ (actually, two 10 kΩ resistors in parallel)

C₁ = 0.001 μF

C₂ = 0.001 μF

C₃ = 0.002 μF (actually, two 0.001 μF capacitors in parallel)

These component values yield a theoretical notch frequency of 16.13 kHz (the very high end of audio range), with the actual measured notch frequency for my circuit (without considering component tolerances) being 15.92 kHz.

I recommend setting the function generator output for 1 volt, to make it easier for students to measure the point of “cutoff”. You may set it at some other value, though, if you so choose (or let students set the value themselves when they test the circuit!).

I also recommend having students use an oscilloscope to measure AC voltage in a circuit such as this, because some digital multimeters have difficulty accurately measuring AC voltage much beyond line frequency range. I find it particularly helpful to set the oscilloscope to the “X-Y” mode so that it draws a thin line on the screen rather than sweeps across the screen to show an actual waveform. This makes it easier to measure peak-to-peak voltage.