The thing that makes Tesla such a compelling, yet
sad case is that he was genuinely brilliant and had carved himself a real place in
history with his accomplishments. His contributions to the field
of electrical engineering are on a scale to rival that of Edison and
Steinmetz and we enjoy the fruits of his labours every time we flick
on a light switch. However, his lonely work habits, refusal to
write things down, and flat-out eccentricities have made him one of
those figures that historians cross the street to avoid.
AC Induction Motor
Tesla's first great invention was the AC induction motor. For
those of you who weren't paying attention in science class, an electric
motor works by flipping the field of an electromagnet, causing the
attraction/repulsion of the magnets to spin the armature around.
The sort of small motors that you see in things like toy cars do this
with metal brushes that touch two metal semi-circles. As the
armature spins, the brushes touch one semi-circle, then the other, and
each time the electrical current in the armature reverses and
therefore its magnet poles do so as well, so the armature spins 'round
and 'round like a puppy chasing its own tail.
Tesla was the first inventor to come up with a practical way of using
AC power to achieve the same reversal of polarity; only this time it's
done with clever wiring. Unlike DC, where the electrical current
always flows in one direction, AC current flows in both directions.
By wiring some the magnetic sections of the motor one way and then their
neighbour sections in reverse, the polarity would reverse
automatically with the current.
Of course, the trick was how to supply current to the armature itself
without burning out the contacts with the high voltages that AC power
required. Tesla's answer was to use induction. That is,
whenever AC power reverses itself, it causes an electrical field to
collapse and re-establish it. When this happens, power is
transmitted. It's what allows certain makes of cordless
toothbrushes to recharge without being plugged into anything.
You just stick them into a coil in a charger base and the induction
field transmit the power to the brush's battery. It's also the
reason why you don't stand under an AC power line with a steel fishing
rod unless you want a shocking surprise. Anyway, in
Tesla's motor, the induction field set up by the AC current feeds
power to the armature without any direct wiring needed.
But the really neat thing about electrical motors is that if you
get one working you also have a perfectly good electrical generator in
one of technology's rare twofers. An electric motor works by
taking electricity in and turning it into motion. But if you take a
motor and spin it, out comes electricity. All this means that
when Tesla perfected his motor, he was well on his way toward building
a new generation of AC dynamos that form the basis of our modern
electrical grid. Up to that time, the main source of electricity
was DC, which relied on low voltage and heavy amperage. In
practical terms that meant it took a lot of oomph to push electricity
through a wire and one could only transmit power about a mile
from the generator. AC power, on the other hand, used high
voltages with low amperage and therefore could be transmitted over
When Westinghouse bought up Tesla's patents it sparked
commercial war between Westinghouse and Thomas Edison, who was a great
backer of DC. There followed years of bitter propaganda battles,
but in the end the AC system won out and Tesla had his greatest
triumph when the Niagara Falls power
station was built with machines that bore his design and name.
despite his achievements, Tesla never had a very good theoretical
grasp of what electricity actually is. He tended to ignore
developments in physics. In fact, he greeted Einstein's theory
of relativity with downright hostility. For Tesla, electricity
wasn't a thing of electrons and energy states, but of fluids,
vibrations, and harmonics in a system which he seemed to understand,
but which made his explanations the thing of which headaches are made.
Whatever his theory, Tesla still managed to get results. He was
fascinated with high frequency electricity, but mechanical generators
could only go so fast before they started to fly apart, so he
developed devices that could provide higher and higher frequencies
without moving parts. The most famous of these was the Tesla
coil; famed denizen of science fairs and cheap plasma globes the
world over. This high-voltage transformer is
familiar to anyone who has seen an old Frankenstein movie where they
were used to generate the electrical arcs that are apparently
necessary if you're going to be a dedicated mad scientist. They
also produce an electrical field that light fluorescent tubes and
similar devices at a distance; a spectacular parlour trick that led
Tesla down more than one rabbit hole.
interest in high frequency electricity had other benefits. A
number of his circuits were basic to radio technology. Because
he didn't understand how electromagnetic radiation worked, Tesla
thought that sending messages through the air required
transmitting huge amounts of energy, so he never produced a working
system, but his patents did predate those of Marconi by several years
and Tesla was awarded precedence by US supreme court in 1943.