I thought that resistors, like the ones that I buy at RadioShack, could only be used on D/C circuits. I was looking up how to's on electromagnets and found a thread that mentioned using resistors with A/C power. The thread was on this forum but I can't find it now. I am guessing that the post was being very vague and that a power adapter must have been used in the circuit. Not just a resistor. A power adapter, like the ones for USB devices and pc power supplies aren't just transforming the voltage by downgrading it to a lower voltage, they are converting it to DC as well, right? So I'm guessing that that was forgotten to be mentioned. Or are there resistors that are used in A/C circuits? Well, I mean, true resistors, not lamps, etc.