fun with electromagnets

[Nuke]

heres something cool to do the next time a science fair rolls around:

http://hackaday.com/2014/12/04/amazing-sciences-simple-electric-train/

just takes some wire a battery and a few neodymium magnets.

[tetryds]

Haha, I see this going very wrong if it gets stuck.

But is a funny example, just needs a bit of explanation, and some small warns, its a short circuit.

So, if anyone here wants to try that, never leave it running for too long, make sure the magnets are facing the same direction (N-S/Battery/N-S) and spread out the wire so it touches itself as little as possible.

[Nuke]

i dont think you will be able to put the magnets on in the wrong direction, they might flip out on you.

its really a clever example of a linear motor. i wouldn't call it a short circuit, since the current is following the desired path, through the local segment of the coil. if the coil is forming a loop as it is shown in the video then the longer path will have a higher resistance than the short path and will draw much less current (and if its long enough the current will be very low). its equivalent to powering two electromagnets in parallel. the part of the coil between the magnets will generate more heat since it has less resistance (because its shorter) and would allow more current to pass. however as the "train" moves along the track it will give the coil time to cool down so coil heating shouldn't be too much of a problem. also disposable batteries have a fairly high internal resistance, if you tried this with a lithium ion cell 2 things would happen: your wire would glow red hot, and your battery would overheat and explode.

Edited December 4, 2014 by Nuke