For AC circuits, I’ve been starting with some combination of the following
1. Quick orientation to a function generator and then Observing voltage vs time graphs for a function generator operating at 0.1 Hz, 1 Hz, 10 Hz, 100 Hz. Questions to prompt thinking about period / frequency, what knobs control / adjust amplitude, and some questions for us to puzzle at how we would color code the potential difference across the FG over time.
2. Observing what happens when the frequency generator is connected to a bulb operating at the same 0.1 Hz, 1 Hz, 10 Hz, 100 Hz.
–> Predictions here can be useful depending on population. Either way, This is a critical observation that I think is super important for students. Include questions that direct attention to frequency of bulb lighting vs frequency of voltage signal. Why is the bulb lighting twice as often?
–> also include Questions to guide students to model current flow through bulb, think about why the bulb doesn’t appear to change brightness at all when the frequency is set high enough.
3. Challenge: figure out what DC voltage achieves same brightness of the bulb for a given AC setting (assuming high enough frequency for the bulb to appear with constant brightness).
4. Now Using a resistor, predict and then Observing current vs time graph together with voltage vs time. Draw attention to various features, including being in phase with each other.
5. Now switch to Observing voltage and current readings from same circuit using a voltmeter and ammeter that are now set up to measure AC. Questions to compare and contrast measures values to graph values. Questions to prompt thinking about what they might be measuring. Why is it showing a voltage less than the maximum?
6. Some mini lecturing to tie it all together with observations of power vs time graphs for both AC and DC.
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