How is it that I can measure voltage across an unplugged wall wart?
I have a 9V wall wart that's been unplugged for 2 days. I hooked it up to my volt meter with intentions of checking the polarity as I plug it in. Without plugging in the wall wart I attached the meter leads to the exposed wire of the wall wart. It immediately showed a voltage of -10 point something. I was glad to find the wires were backwards which explains my fried regulator; however how is it that I was able to pick up a voltage, even after discharging it the voltage slowly rose again, unplugged! Does this have anything to do with earths magnetic effects on the inductor?