I've seen it before, I was even supposed to learn it last year, but no one has ever explained it well to me. My teacher last year was so... I guess you guys are my only hope.

Also, coud anyone explain why E = qV (electric potential = charge * voltage, sorry if I put the terms wrong as I learned this in french). I get the fact that voltage is J/C and electric potential is J (that's how I do the problems) but I need to.. see it.