Circles of magnetism

From: Nicholas Bodley (
Date: Wed Mar 28 2001 - 09:52:58 PST

Yup, another message.

You *do* need to be careful doing this. A traditional zinc-carbon
lantern battery (if you can find one) might withstand a short circuit
for several seconds, but don't try it with some more modern
batteries, such as gelled-electrolyte lead-acid rechargeables!

Most of all, do NOT use a car battery! The 1,000 amps or more that it
can put out to start a car on a cold morning can give rise to some
unexpected and unwanted effects, including hydrogen explosions.

Zinc-alkaline batteries can put out enough current that you might
find overheating in unexpected places.

Also, avoid modern "high-tech" batteries such as lithium types,
especially rechargeables. Properly-marked batteries will have printed
warnings on them about short circuits.

In any event, this experiment is extremely abusive of the battery;
ideally, plan to do it just once, and only for a few seconds.

What you *really* should do next is to make a multi-turn coil. Use an
automotive ammeter, of the kind you place next to a starter cable, to
show the short-circuit current first, then a conventional auto
ammeter to show the current through the coil. Compare effects...

You might try placing a fractional-ohm power resistor (Radio Shack
should have them) in series to limit the current to something halfway
decent for the battery.

Our society, in general, knows roughly as much about technology as
does a rock; and this pig-ignorance (which you are doing God's work
to banish! :) can lead people to do things they might get hurt by.
Common knowledge about technology is no longer common at all. I'm
sure you know this.

Pigs are far smarter than the expression might suggest, btw, so I'm

Nicholas Bodley |@| Waltham, Mass.
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