PURPOSE: To demonstrate charging of a capacitor in a possibly counterintuitive way.
DESCRIPTION: A knife switch is closed to charge a 1 farad (yes, one FARAD), 5 volt capacitor with a 7.5 volt battery. Oh, yes, the capacitor has 10 volt light bulbs on each side of it in the circuit, as shown in the drawing below. Q: What will happen when the switch is closed: (a) both bulbs will light and stay lit, (b) both bulbs will go on momentarily, (c) only one bulb will light and stay lit (if so, which one?), (d) only one bulb will go on momentarily (if so, which one?), (e) neither bulb will go on at all, (f) something else will happen (if so, what?). A: Both bulbs will go on momentarily as the capacitor charges, then go off. Q: What will happen when the switch is opened? A: Nothing, but the capacitor remains charged.
SUGGESTIONS:
EQUIPMENT: 7.5 volt battery, 1 farad 5 volt capacitor, knife switch, two 10 volt light bulbs.
SETUP TIME: 5 min.
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