Monday, December 12, 2011

Homopolar Motors

The required service project that I chose to be a part of is getting local sixth graders excited about science so that eventually they will come to this school.  We are given a theme and put together a presentation that shows how cool science is.  This time the theme was chemistry.  Since they were sixth graders I allowed myself some scientific license to make that theme fit with the concept of electromagnetism.  I've always wanted an excuse to buy some neodymium magnets and this was the perfect opportunity.  The result was 12 fifteen minute presentations of wide-eyed kids.  This guy explains the assembly.

The magnets are pretty cheap, but you can only get them online.  The entire magnetic field of the earth is only about 10^-4 Teslas and these little guys are about 0.75 Teslas.  If you try this at home, let me warn you: take all precautions that your fingers don't get caught.  For each unit that the magnets get closer to each other, the force between them increases by a square.  You will be tempted to wrestle them away from the trapped flesh, but that only decreases the amount of flesh between them leading to a stronger pinch.  Also, the material is very soft and the attraction is very strong.  If you let them smash together, the magnets will shatter and you will be left with magnetized shards.  One last thing, don't swallow them because nothing can be worse than a kink in your intestines.  All of that aside, enjoy responsibly!

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