Here is a decent page on it http://www.howstuffworks.com/question501.htm and here is a good page on OHM's Law http://www.grc.nasa.gov/WWW/K-12/Sample_Projects/Ohms_Law/ohmslaw.html -sean who says I didnt learn anything from school > Hmmm... amps, volts, watts ..., I know I've got an old text book around here > somewhere that will detail the conversion.