This is from a book I am about to start pitching:
Hans Oersted is remembered in the name of the unit of
magnetic field strength, the oersted. He was also the person who coined the
term ‘electromagnetic’. With that sort of introduction, it should not be hard
to work out that it was Oersted who first observed the magnetic effect of an
electric current. All the same, Oersted was trained in metaphysics (a branch of
philosophy), rather than in physics.
Nonetheless, in 1806, he became professor of physics and
chemistry at Copenhagen. As well as being the first to prepare metallic
aluminium, Oersted is remembered for his discovery of electromagnetism, which
he made during a lecture. His discovery of the electromagnetic effect was
immediately translated into several languages, though not entirely reliably.
The 1826 English source I found for his work contained a contradiction which
was not in the 1820 French version I happened to have to hand, so my quotation
below is a mix of the two versions.
If he had written in Latin, and we had all been forced
to learn Latin, this problem would not have arisen, but even by the 1820s,
Latin was no longer universally understood.
The first experiments…were set on foot in the classes for
electricity, galvanism and magnetism, which were held by me in the winter just
past. By these experiments it seemed…that the magnetic needle was moved from
its position by the help of the galvanic apparatus…when the galvanic circuit
was closed, but not when open, as certain very celebrated physicists in vain
attempted several years ago…
You can see the way this worked in the illustration above,
but as this is simple enough for the reader to try, let me note that the entire
apparatus is one compass, one AA cell, a length of insulated wire and some
sticky tape, plus an aluminium ruler which is optional, but it would have
pleased Oersted. I bared one end of the wire, taped it to one end of the dry
cell (this was sloppy practice but good enough) and bared the other end.
I taped the dry cell to the ruler (or to the rule if you
are a pedant), taped the compass to the ruler to stabilise it, and that was it.
As you can see, a single dry cell was enough to bring about a noticeable swing.
Incidentally, if you reverse the wire (and as a result, the current), the swing
reverses, and the same reversal happens if the wire is under the compass.
One of the great continuing arguments in science relates
to the need to justify research in advance, usually for the benefit of bean
counters, weasels and other parasites, by showing what research is useful for.
Even the most useless-looking piece of science can become useful, as Karl
Pearson was to discover. Here, Lord Kelvin reflects upon Oersted’s researches:
Oersted would never have made his great discovery of the
action of galvanic currents on magnets had he stopped in his researches to
consider in what manner they could possibly be turned to practical account; and
so we would not now be able to boast of the wonders done by the electric
telegraphs. Indeed, no great law in Natural Philosophy has ever been discovered
for its practical implications, but the instances are innumerable of
investigations apparently quite useless in this narrow sense of the word which
have led to the most valuable results.
—Lord Kelvin (1824–1907), 1846, quoted R. A. Gregory, Discovery (1916),
241.
Aside from Luigi Galvani and Alessandro Volta, the main
players in the unravelling of Faraday’s electromagnetism include Georg Ohm,
Hans Oersted, and James Clerk Maxwell, who brought us to the point where we
could see light as an electromagnetic wave, much as Michael Faraday had
expected, leading on to George FitzGerald, and then to Heinrich Hertz,
Guglielmo Marconi and beyond.
There are also the users of electricity and magnetism,
from Joseph Henry and Edward Davy, who both invented an electric relay, Charles
Wheatstone, Alexander Graham Bell, and people like Joseph Swan, Thomas Edison
and Nikola Tesla who made our modern uses of electricity possible.
There was far more to magnetism than compasses for
navigation. After Oersted found that a variable current in a wire would make a
compass needle deflect from its usual direction, André Marie Ampère
(1775–1836), found that like currents attract, then he discovered the solenoid
in 1826: this was a coil of insulated wire with a current passing through it,
and it would be the basis of transformers, electric motors, relays and
electromagnets. The most common and audible household use of the solenoid today
is probably in the switching systems which commonly turn the water flow on and
off in washing machines.
Ampère completed his work while believing incorrectly in
two ‘magnetic fluids’, which he called a northern fluid, and a southern fluid.
So long as he observed correctly, and so long as his theory allowed him to make
sensible predictions to test, it mattered little. Then in 1831, Michael Faraday
discovered electromagnetic induction, and soon after, invented the very first
electric motors.
Following on from this in 1845, Faraday discovered what
we now call the Faraday effect, where a magnetic field makes the plane of
polarised light rotate. This later influenced James Clerk Maxwell to come up
with the idea of electromagnetic radiation, which led to Hertz inventing radio.
And it all came from one simple observation by Oersted, a lifetime earlier!
Science is like that…
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