I have a small screwdriver which has a small LED in it. When you stick it into something like an outlet, and hold your finger on the other end, the LED lights up. Today though I held both ends of the screwdriver and the LED lighted up. This confuses me tremendously... Doesn't that indicate there is a potential difference between the two fingers? Otherwise what makes electricity flow and light up the LED? Does anyone know these screwdrivers? My best hypothesis is that it must have a battery in it or something, and some type of a small ammeter or something?