Any Engineers here? - magnet content

DaveH

DaveH

Joined
Dec 2, 1999
Messages
12,249
I found a youtube video last night, and having just bought some rare earth neodymium magnets, I had to give it a try. Below is a picture, 1 "D" battery, a small length of wire, 1.5 inch drywall screw and a magnet. The wire is connected to the battery and the other end is brushing the periphery of the magnet It doesn't show but it spinning.

rem_motor.jpg


Nail size and placement is critical, just the point can touch, too short and the magnet sticks to the battery, to long it falls off. Magnet is not critical, I tried 3 different sizes all worked well. It can wind right up, I tried it with a 9 Volt and it sings, 9v got a little hot though, makes sense because it's a dead short.

The question I have is why does it work? I imagine that at the instant of electrical connection the current flow sets up it's own field on the surface of the magnet which interacts with the magnet's field and causes a rotation. Continous brushing connection creates additional fields and rotation. I'm having trouble getting a mental picture of the field produced that causes the rotation.
 
DaveH said:
The question I have is why does it work? I imagine that at the instant of electrical connection the current flow sets up it's own field on the surface of the magnet which interacts with the magnet's field and causes a rotation. Continous brushing connection creates additional fields and rotation.
Click to expand...

That's exactly why it works.
 
You just made a simple DC motor. That stuff has facinated me since I was five yrs old and still does.
 
What's so amazing to me is how simple it is, no wires to coil or anything. Of course the surface of the magnet being conductive is key.

My local hardware store now carries rare earth magnets at prices competitive to the web though their selection is not great.
 
Have you got nieces and nephews? A local scout troop? A church group? When I was a kid, I would have loved to have an adult around who was interested in that kind of stuff. Just watch out for the bigger magnets. They can do a really nice job of crushing your fingers.
 
Well, I do have kids and cubscouts who would love to see stuff like this. Where is a good source to obtain these magnets?
 
I bought magcraft through amazon because I had a gift certification.

Besides ebay, magnets:

http://www.gaussboys.com/
http://www.wondermagnet.com/
http://www.rare-earth-magnets.com/
http://www.kjmagnetics.com/categories.asp
http://www.supermagnetman.net/

Motors links:

http://www.coolmagnetman.com/magdcmot.htm

Experiments:

http://www.coolmagnetman.com/magindex.htm
http://amasci.com/neodemo.html

BTW, I dropped some magnets down a 1 foot length of copper pipe, it took maybe 5 seconds to fall through. Very cool.

FYI, If young kids I would suggest not getting anything bigger then .5" by 3/8 thick. That's what's in the pic above. I have some .5 by .5 and got bit a few times even when trying to be careful.
 
Brings back the fun of younger days.

As Maxwell's Equations state, a moving charge creates a magnetic field and a moving magnetic field can create a moving charge. A vastly oversimplified statement, true, but correct in its essentials.

Try suspending a strong magnet above a loose, conductive surface. Spin the magnet and you will inevitably see the conductor below start to spin as well.
 
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