I'm going to go under the assumption that whatever I say is right, even though I know it's probably wrong (it saves me phrasing the entire thing as dozens of questions that way), so... correct me where necessary: If I have a +X volt battery and I connect it up to a circuit with an LED in it (forward biased), and the LED itself has a switch-on voltage of +X volts, then it will light up. However if I have the same circuit, but reverse biased, it won't work. Now, if I say my battery is a -X volt battery (the LED still needs +X volts to switch on), is this not the same as saying that it's a +X volt battery, except with the current flowing in the opposite direction? If so, would a reverse biased LED with a switch on voltage of +X volts switch on if the voltage of the battery was given as -X volts? I don't think I'm wording it very well, but... hopefully someone gets what I'm asking. I asked my physics teacher and he said no, however I don't know if he's understanding what I'm trying to ask, and, well, he's not done this stuff in years. He could be wrong.