Most recent answer: 10/22/2007

I made one of the nail electromagnets by wrapping tons of thin wire around a nail and hooking it to a some spare ac/dc converters around my house. well a four and six volt out put barely did any thing, but the next step up was 24 volts, so I tried that and it worked, but then the thing short cuirted, I think. so my question is how do I know how much voltage to put through my magnet?
- nate (age 17)
chandler high school, arizona
It sounds like your magnet had a pretty convenient resistance, since it worked best with a safe voltage in the range for which power supplies are cheap and easy to find. Probably you fried the insulation by getting it too hot. When you stepped up from 6V to 24 V, you multiplied the heating power by 16. It would be best to increase the voltage by smaller steps, and to feel the coil to see if it’s starting to get hot. If it is, reduce the voltage.

Lab electromagnets often have thin water coils built in so they can be cooled with running water. That might be difficult for your set up. You might at least try to make sure that your coil is spread out over the whole nail. You may also be able to insert some aluminum cooling fins.

Mike W.

(published on 10/22/2007)