Extract batteries from stubborn holders
We've all got things that take batteries. Some of them are well designed, and some of them are not. The worst offenders are electronic toys that take (say) half a dozen AA batteries, all of which must be inserted with the correct orientation-- spring side first-- and pried out, well, somehow. Rather than risk puncturing your batteries by prying them out with something pointy, just use a magnet to lift them out.
| Find studs in your walls Move a magnet over the wall until it finds a screw or nail head under the paint. You don't even need to mark the wall-- you can just leave the magnet there until you've drilled your holes. |
| Make a homopolar motor One of our favorite demos of all time is a homopolar motor. A magnet, a wire, a battery and a screw are all you need to make a motor spin up to 10,000 rpm. | 
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Make LED Throwies
LED throwies are useful for many more things than graffiti. We've made variations from garden lights to origami to greeting cards, but it's not a real throwie without a magnet.
| Demonstrate magnetohydrodynamic propulsion You can make your very own caterpillar drive like the one in The Hunt for Red October with this magnetohydrodynamic demonstration. |
Available from K&J Magnetics, this is enough magnets to really have some fun. More magnet sources are in our links section.
| Make a simple compass We've previously shown how to make stupidly simple compasses that float on water or spin on a smooth surface. Here's another method: sandwich a thread between two very strong magnets and hang it down for an instant compass. | 
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Experiment with self assembly
In a process that is a lot like assembly of biological molecules or crystal formation, randomly ordered magnets can almost automagically form themselves into neat chains. Here are some magnetic self assembly videos.
| Make almost anything (ferromagnetic) into a building set With magnets as connectors, you can build tins into anything you like. (Just be sure to get Bawls Mints, not Bawls Buzz). | 
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Make a Curie motor
A Curie motor uses heat to demagnetize an area of a magnet, causing it to move away from the heat where the cycle starts again. On BoingBoingTV, Mark Frauenfelder shows you how to build one with a candle, a wire and a couple of magnets.
| Freaking awesome chip clips Fold over the open top of the bag and put magnets on either side to hold it closed. |
Play with eddy current damping
Drop a magnet down an aluminum or copper tube, and you'll see a hovering slow fall caused by eddy current damping. Here's a quick video.
| Make a fridge pen Slip a small magnet underneath the metal clip on a pen (these uniballs are our favorite) and you can keep a pen handy on the fridge for your shopping list and phone messages. | 
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Defeat magnetic safety interlocks
All kinds of cool industrial machines from photocopiers to deep fat fryers have magnetic safety interlocks to prevent the machine from working with the cover open. Whenever you see a magnet attached to a hinge, it's there to protect you. So if you ever want to do something ridiculously dangerous like laser engrave your fingernails, you'll need magnets to disable the magnetic interlocks.
 | Make anything into a fridge magnet We like to make unusual things into fridge magnets. And this trick has occasionally fooled folks into trying to open our fridge magnets to look for candy. |
Demonstrate diamagnetic levitation
By placing diamagnetic material (such as bismuth or graphite) between a large magnet and a small one, you can levitate the small one. Detailed instructions and links to kits for this are on Bill Beaty's site, amasci.com.
Wake up your laptop or put it to sleep
Many laptops have a magnetic switch that tells the computer to go to sleep when the lid closes. Older Macs could be fooled into going to sleep with their lids up by waving a magnet by the upper right hand corner of the lid. Newer Macs can be fooled by resting a magnet on the switch on the right hand side of the keyboard. Caution: don't put a magnet near your hard drive!
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