So how goes the project? Any news?
Not to keep harping, but here’s another way to use a Joule Thief:
Get the students to bring in their favorite 2-cell flashlight. Have each one build a 1-cell Joule Thief & mount it in a cell-sized “dummy” for their own favorite flashlight. I’d guess you’ll also have them take a burned-out bulb, trim the glass & filament off & install some LED or another on the Base. Obviously great care is required!!
Now, they’ll have an “energy conserving”* flashlight that only uses one battery at a time instead of two.
All you’d need is one white LED, one wee toroid, a couple of feet of wrapping wire, a decent transistor, maybe a resistor (please not 1k!! — use of a pot will show you how little resistance you actually need) and tubing to make dummy cells; per each. I think they’d get a lot of insight during the testing & tuning phase as they add & remove turns on the toroid & observe the results in light output & runtime (assuming you have time to test runtime).
You could offer extra “credit” for anyone who gets it working with an incandescent bulb…
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* “Energy Is Conserved”
~ Rudolf Clausius