What the heck is a Tesla Coil, anyhow?
2012 W. Beaty

What is a Tesla Coil?

It's a resonator.

But it uses electromagnetism, not sound. So there's our top definition right there: A TESLA COIL IS AN ORGAN PIPE FOR RADIO WAVES.

A Tesla Coil is a spiral made of wire, either in the form of a cylinder, a pancake, or cone. So very simple.

And yet ...not.

A Tesla Coil is a kilowatt radio transmitter, called by Marconi "the Spark Transmitter" (see what he did there?) Spark transmitters (Tesla coils) were very famous at the dawn of radio during the Morse Code era. They made communication possible across oceans and between distant countries. I mean, spark transmitters became famous. Not Tesla Coils. Even though they're the same device: a grounded spiral of wire with a high-volt power supply and a spark gap. Everyone knows that Marconi invented the spark transmitter, while "Tesla Coils" are only good for making lightning bolts in Frankenstein movies, (unless you give the lightning machines the name "Spark Transmitters" and walk away with the Nobel Prize.)

A Tesla Coil is for making physics departments look bad. In the 1890s, academia was in the "Mine's Bigger" stage of Induction Coil development. Pursuing first prize of one million volts. The stature of any major laboratory could be rated in inches of spark they could achieve. This was similar to the 1930s, when universities were rated in inches of cyclotron diameter and number of Mega-electronvolts. But Tesla's early versions gave out sparks which were THREE TIMES LONGER than the top physics departments. Who's your daddy?

The induction coils in physics labs used hundreds of thousands of turns of wire. Tesla's own coils used about a hundred turns.

A Tesla Coil can be used as a step-up transformer, but Tesla himself distained this notion. In fact, the high voltage actually comes from resonance, not from the high turns-ratio as with induction coils. Tesla preferred to use them not as transformers but instead as single stand-alone coils. Just a coil, no "primary and secondary." He'd drive them with high voltage AC through the "ground wire" at the base.

It's an AC power supply used for many things besides transmitting radio. It's a source of extreme high voltage, but unlike the VandeGraaff machine, it's capable of hundreds/thousands of watts output.

A Tesla Coil is basically the same as a Vandegraaff Electrostatic Generator, but one for AC instead of DC.

It's a way for early science labs to achieve electric potentials far above one Megavolt

It's a high-wattage RF generator useful for industrial induction heating and plasma processing

It's a waveguide, but not for microwaves. Instead it works at radio frequencies in the longwave bands.

A Tesla Coil is a waveguide of a certain particular length; intended for storing intense standing-waves inside.

Tesla coil: a Victorian switching power supply. Well, actually Edwardian I guess.

It's the power supply used to create the high-volts in all CRT-based video displays.

It's the high-frequency spark generator found in automobile ignitions.

It's the power supply for those "plasma globe" art devices.

It's the power supply for CCFL bulbs and fluorescent tubes (every LCD laptop display has a tiny tesla coil running its LCD backlight)

And finally, a Tesla Coil is a mega-engineering tool appearing in the illustrations for Tesla's popular articles in magazines. But today we have no idea how Tesla planned to use it do the things depicted. "Believers" are convinced that Tesla had some novel ideas he kept secret. But rest of the modern engineering and scientific communities are sure he had no such ideas, and that his only secret was that he'd gone crackpot, and his ideas didn't actually work. But both sides of this fight are speculating, since we never actually funded Tesla to prove his "exaggerated" claims. His 'exaggerated' AC motor claims turned out real, as did his crazy AC grid, as did the Tesla coil (spark transmitter) taken and used for worldwide broadcasts. All were derided by top experts of the time, directly violated contemporary physics, and only prevailed against opponents because they were built and operated.


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