Wonders of physical scienceFournier d'Albe, E. E. (Edmund Edward)
General
Wonders of physical science
Fournier d'Albe, E. E. (Edmund Edward)
Physics -- Juvenile literature
But however long the current was kept passing through the first wire,
the galvanometer showed not the slightest current in the second wire.
This appeared very strange, because it was known that bodies may be
made electric, or magnetic, by bringing them into the neighbourhood
of electrified or magnetised bodies. It was natural, therefore, to
suppose that a coil of wire could be made to carry an electric current
by bringing it into the neighbourhood of another coil of wire which was
already carrying an electric current. But in such things it is useless
to endeavour to answer questions offhand. The only proper way is to try
an experiment. Faraday did try the experiment as already described, and
the result showed him that he was mistaken.
But Faraday was not discouraged easily. Thinking that perhaps the
effect could be strengthened by winding the wires round a piece of soft
iron, he took a ring of iron and wound two coils of wire round it,
taking care that no part of the wire was touching any other part, or
touching the iron. He then observed a curious effect, which was quite
different from what he had expected. He found that the galvanometer
gave a little start as soon as he turned on the current in the first
coil. Then it came to rest again, although the current was still
flowing. On turning off the current, the galvanometer gave a little
start in the opposite direction, and soon returned to rest again.
Faraday was in doubt whether this was really such an effect as he had
been looking for. He wrote to a friend, “I think I have got hold of a
good thing, but cannot say. It may be a weed instead of a fish that
after all my labour I have at last pulled up.”
Faraday was a first-class experimenter, and his method is a good
example of truly scientific work. When he found an effect which he
could not quite account for, he changed the experiment in a great many
different ways, in order to disentangle the causes and effects. The
next time he tried to obtain a current by means of a magnet instead
of another current. He took a natural magnet and wound a long coil of
wire round and round it. The natural magnet had a cap of iron, and on
pulling the cap off, a short momentary current appeared in the coil of
wire. This momentary current could be shown either by attaching the
ends of the coil of wire to a galvanometer or by bringing them close
together. When that was done a small spark passed between the two ends
of the wire.
Public-domain text, read in full here on John Shaqi.
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