Lefty: Thank you for correcting me on my use of "NPN." I'm about 2-3 months into electronics and almost a month into Arduino. I clearly have a lot to learn. There are no electronics classes at my high school so I'm doing everything on my own. It's really cool to show successful projects to my teachers because they are in awe, but it's a huge pain in the ass when I need help because no one there knows enough to help me out. As far as my schematic goes, is this correct? http://www.flickr.com/photos/brandondub/8428978072/in/photostreamYour drawing is correct, except for forgetting about the all important ground wire from an arduino ground pin to the negative terminal of the battery. Also, probably an idiotic question: I don't need a pull down resistor on the gate here because the Arduino will write LOW when told so, but if I was just using an SPST switch it would need an in-circuit pulldown, correct?Not a idiotic question at all, but rather an insightful one. Yes a 10K ohm resistor wired directly across the source and gate terminals would insure the mosfet turns off when there is no signal going to the gate terminal. Some people advise to wire that in even when using an arduino in that there might be a case where your arduino is powered off but the battery is still available to power the magnet and without an active low coming from the now unpowered arduino the mosfet may not stop conducting.Have you dealt with how much current your magnet draws when being powered via the battery?