This device makes an
attractive advertising sign.
** A Floating Electromagnet [152]
A piece of iron placed in a coil of wire carrying a current of
electricity becomes an electromagnet. If such a coil and iron core
be made small enough they can be attached to a cork and the cork,
floating on a solution, will allow the magnet to point north and
south. The sketch shows how to make such an instrument. A coil of
insulated wire is wrapped around a small iron core, leaving a few
inches of each end free for connections. The insulation is removed
[Illustration: Floating Electromagnet]
from these ends and they are run through a piece of cork. Attach
to the wires, on the under side of the cork, a piece of zinc to
one end and a piece of copper to the other. The cork is then
floated on a solution of acid, with the zinc and copper hanging in
the solution. If zinc and copper are used, the solution is made
from water and blue vitriol. If zinc and carbon are used, the
solution is made from sal ammoniac and water.
The float will move about on the solution until the magnet iron
will point north and south.
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