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Q:
All your instructions on making magnets start either with an existing magnet, or an electric current. I have read that Faraday discovered magneto-electric induction by attaching two wires through a sliding contact to a copper disc then rotating the disc between the poles of a horseshoe magnet he obtained a continuous direct current, the first generator. The big question is, without an existing current - i.e., without a generator, how did Faraday create the horseshoe magnet?
- Vincent (age 66!) (age 66!)
England
A:
Great question.
My answer for now is just a guess. If you Google around, you
should be able to get a real answer from someone who actually knows
some history. There are a couple obvious possible ways. One is that we
happen to be sitting on a big magnet, the Earth. As magnetic rocks
cool, they magnetize because of the Earth's field. So maybe Faraday
just used some natural magnetic rocks. These exist- that's how
magnetism was first discovered. The other possibility is that he helped
magentize something using electromagnets driven by batteries. If he had
a nice horseshoe, I'd guess he magnetized it with current from
batteries. Come to think of it, that's very likely because the pattern
of magnetism in a horseshoe magnet isn't what you'd get from cooling it
in field as nearly unifrorm as that of the Earth.
Mike W.
You could cool a straight iron rod in the Earth's field and then
when it's cold, bend it around in the shape of a horseshoe. Just a
speculation, though.
Working electromagnets were made by Joseph Henry earlier than Faraday's primitive dynamo.
Tom
(published on 10/22/2007)
Follow-up on this answer.
