At the Palais de la Decouverte in Paris, they showed me this experiment
where a 1kg aluminium plate is levitated above a large coil of wire that
is being supplied with 800A of alternating current at 900Hz. This is by
far the best demonstration of electromagnetic induction I have ever
Back in London, I visited the magnetic lab of Michael
Faraday in the basement of the Royal Institution. It was here that he
did his groundbreaking work on induction. People had previously observed
that current in a wire causes a compass needle to deflect, but more
exciting was the prospect of using a magnetic field to generate current.
Faraday created his famous induction ring by winding two coils of
insulated wire onto an iron ring. When he connected a battery to one
coil, a small pulse of current was induced in the other. When the
battery was disconnected, current was induced in the other direction.
This led Faraday to the conclusion that current was induced in the
second coil only when the magnetic field through it was changing.
if they hadn't been wrapped on the same ring, Faraday may have noticed
that the two coils repel each other when the current is induced due to
the interaction of their magnetic fields. This is the same thing that is
happening with the aluminium plate, except we're using alternating
current to create a continually changing magnetic field. This induces an
alternating current in the plate, producing an opposing magnetic field
which levitates the disk.
no idea what any of that means
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