Physicist: Stripped down to it’s most essential parts, a Tesla coil is a wire sticking out of the ground. To get sparks to fly out of the top the rest of the machine “sloshes” electrons up and down the wire.
The picture you should have in your head is a long bathtub, open to the ocean on one end. The machinery of the Tesla coil is like some dude in the bathtub sliding back and forth, splashing water (electrons) out of the closed end, while the tub is refilled from the ocean (ground).
The electricity in the primary coil is what’s doing the pushing, and the electricity in the secondary coil is what’s being pushed. To understand how the driving mechanism works requires a new metaphor and some answer gravy.
Aside from inspiring fear, Tesla coils are useless. Truly, Tesla was a genius. The strange shape is an attempt to avoid arching from the torus to the primary coil, which is bad.
Answer gravy: To get sparks to really fly you need very high voltage (up to several million volts) at a fairly exact frequency. The current that flows up and down the secondary coil, and sloshes out the top, has a high resonant frequency (~MHz, unless the coil is ridiculously huge) that you really can’t do much about. But the current coming out of the wall has a frequency of only 60 Hz (50 Hz for our Old World readers).
One possible circuit configuration for a Tesla coil.
So how do you change frequencies? The answer is you “pluck” the primary coil. For example: If you pick a guitar string once a second you have a frequency of 1 Hz, but the string vibrates on its own at whatever frequency it’s made for (~10 kHz).
The AC mains have a low frequency (60 Hz) while the secondary coil needs to be driven at a high frequency (~1,000,000 Hz). That means that the secondary will slosh back and forth thousands of times every time the current from the wall turns over just once. Since the fast part of the circuit is so much faster than the slow part, you can just pretend that the current from the transformer is DC (direct current = 0 Hz).
The secret to plucking is to change the circuit’s “shape” using a spark gap. Spark gaps have some pretty slick properties. They have an essentially infinite resistance until a high enough voltage is applied across them, at which point they spark (hence the name). The spark you see is the air being pulled apart and ionized. Now ionized gas is a really good conductor, so a spark is like instantly closing a switch.
Also, spark gaps are the cheapest circuit element evar. Can you cut a wire? Now you got a gap!
Also, adding spark gaps to a device is one of the quickest ways to bridge the divide between regular and mad science.
The transformer on the left forces charge to build up in the capacitor on the top. But the voltage across a capacitor is proportional to the amount of charge it's holding, so eventually the voltage is high enough to trip the spark gap.
The only job that the slow part of the circuit has is to charge the capacitor (pull back the string). When the spark gap sparks (pluck!) the fast part of the circuit takes over, and the slow part is essentially ignored until all the energy is exhausted by exciting the secondary coil (string vibrates and slows).
With the spark gap active the charge can flow out of the capacitor and swing back and forth many times, very fast (thousands to millions of times per second). The current through the primary coil then drives current up and down the secondary, causing electrons to "overflow" from the top of the Tesla coil. The "overflow" is a delight to children of all ages.
As current flows through the primary it creates a voltage across the secondary that’s so high that electricity actually flies out of the top of the coil, despite having nowhere in particular to go. It generally takes at least several hundred thousand volts to make that happen.
The loop in the picture above forms an RLC circuit with a high resonant frequency (that matches the frequency dictated by the secondary). As the energy in this system runs out the voltage needed to maintain the spark gap (which is much less than the voltage needed to start it) is lost, and the whole thing returns to the slow, charging phase.
Since the power supply oscillates at 60 Hz, the whole system briefly turns off 120 times every second (the voltage is +, 0, -, 0, +, 0, …). For this reason Tesla coils have a very loud 120 Hz hum that sounds “staticy” and ominous, as opposed to Jacob’s ladders which are continuous, and tend to sound more like “tearing”. Connoisseurs, I’m sure, will agree.
nikola tesla is awesome
Tesla – “father of A.C”
I LOVE NIKOLA TESLA SOOOOOOOO MUCH <3 <3
P.S Hey Niko, lets go bowling.
How is the tesla coil useless? The original design was to power the world wirelessly and for free. At his lab in Colorado Springs he used a tesla coil to power lamps 25 miles away!
You can’t power anything for free. The energy you transmit still has to come from somewhere.
Either way, a Tesla coil doesn’t transmit power. It a big, loud, dangerous toy.
well, according to what i’ve reseached about tesla coils, you could theoretically creat a self sustaining generator, of course my math is probably wrong but its an interesting idea
i just thought i should mention, you are wrong sir when you state the Tesla coil does not transmit power.. how can you deny the fact that it can, and does? would lighting an incandescent bulb via a wireless field not constitute transmission of power? i’ve done it myself. maybe you mean it does not transmit “free” power, in which case i would agree.
The thing that got Tesla excited about coils and power transmission wasn’t the ability to magically pull free energy of of nowhere (that can’t actually work) and more about using the magnetic fields from ridiculously high voltages to cut down on the gradually accumulating power losses you get when you pass electricity through really long power lines.
Perogie, what you describe, the self-sustaining generator, wouldn’t work. It is a Perpetual Motion Machine of the First Kind. Tesla coils can accumulate very high voltages, from much lower ones. In exchange, however, they must slow the current down to a crawl. Power is the voltage (how much energy each electron packs) multiplied by the current (the number of electrons passing through a point each second). Your losses in current will more or less exactly cancel out your gains in voltage, for no net change in power.
Well, technically, you’ll still lose power to inefficient transformers and any incidental wire resistance, but you see what I mean.
I built one of these with my son last year. The input
Is a 30 ma 15kv neon transformer. There are about 12
Winds in the primary, and 1200 in the secondary,
Making the ratio 100:1, so the voltage is stepped up
To 1.5 million volts. It produces a ” lighting bolt” of about
3 feet, depending on how I “tune” the spark gap. We have
A fan right at the spark gap to quench it, and it needs to be
Cleaned from time to time. If its in the back yard, it will
Light a fluorescent bulb from up to 15 feet away, and is quite
Loud. Although Tesla’s coil is incredibly inefficient, ( think of the
Resistance encountered when trying to “electrify the world”), loud, (probably
About 100 dB for our medium coil), and dangerous (imagine havong a
Pacemaker next to one of those things) it does, in fact,
Work. Tesla is by far the most under estimated, under compensated, and
Misunderstood inventor of all time, and my favorite by a long margine.
I’m glad he finally got credit for the invention of radio in 1943. Too bad
He wasnt alive to receive it.
The Physicist is obviously NOT a physicist but instead a frod. To imply the tesla coil does not transmits power is like saying a light bulb does not emit light. Physicist either go get your degree in physics or stop being a dumb***.
Admittedly a Tesla coil transmits power in very much the same way that a light bulb emits light energy, or a stereo (or even a ticking clock) emits sound energy. You can even harvest that energy from a distance. However, the amount of energy you can collect is tiny compared to the amount of energy that went into powering the coil. In very much the same way that the amount of energy you can collect from a light bulb using solar panels is tiny compared to the energy that goes into lighting the bulb.
So, sure, a Tesla coil transmits power in the same sense that effectively every functioning machine transmits power. But that’s not really what it’s designed to do.
It seems you’re wrong again Physicist. The Tesla Coil was designed by Tesla to be a part of his “World System” of power transmission. He wrote all about this in numerous papers as well as in his autobiography “My Inventions” which can be found at
http://www.lucidcafe.com/library/96jul/teslaautobio.html
I don’t know why people insist on belittling his vision and the true power of his inventions. The Tesla Coil was one part of an array of devices which would have had world-changing implications. Tesla himself states that his World System was tested, proven, and all it lacked was to be implemented. His only regret was perhaps that such great leaps in harnessing the power of Nature might lead destructive and disunited human wills to obliterate each other on massive “World” scales.
When we look at the Tesla Coil as an independent unit of invention, we perhaps only see its independent operation. But make no mistake, Tesla knew how to use it along with his other inventions to harness the very power of the Earth and the Sun, and perform feats which many today cannot even begin to fathom.
When primitive man first looked at the Sun, he perhaps said something like “That disc does nothing more than provide us with pretty light and warm heat.” But as we began to pierce the veil of Nature, we discovered the wonders of photosynthesis, solar winds, even gravity itself holding us in orbit, and operating our artificial means upon that discovered Nature, mankind has developed himself and every technology to its current state.
We need some great minds like Tesla to arise in our day, to wake up to the awe in Nature as he did, and resolve to lift her veil, understand her mysteries, and through art, harness her powers towards the evolution and union of Man.