Tesla Coils

June 14th, 2010 by Sergio de Biasi

Artificial lightning on demand

In my previous post about Kirlian Photography I ended up briefly discussing high voltage generation methods in the comments. Now, one of these methods involves what are called Tesla coils, which use a resonant transformer to operate. And since I did experiment with them in the past, I decided to post some pictures here. In the first picture above, which was taken in the dark, one can very clearly observe the glowing plasma that is generated when we create such a high difference of electric potential between a pointed needle and a metal plate that electrons simply jump from one to the other, ionizing the intervening ambient air in the process.

The same setup with a longer exposure

Tesla was actually a very interesting character. He was undeniably a first class genius and in the field of putting electricity to practical use it’s very arguable that he was as relevant as the much more widely celebrated Edison. In fact, he is one of the Nobel Prizes that weren’t meant to be – he was nominated but due to several political isues, including the strong animosity between him and Edison, never won.

I believe there is a very illustrating (and somewhat depressing) clash of personalities to be observed here. Edison’s first invention was a vote recording machine, which he successfully developed, tested and proudly patented. Unfortunately, it was an engineering success but a complete commercial failure. So he decided never to spend efforts again developing something that he couldn’t sell, and dedicated the rest of his very successful life to relentless and agressive promotion of commercial applications for his inventions. Tesla, on the other hand, was much less concerned with developing effectively marketable products, and although he did have many immensely useful ideas with very practical applications, his heart was not really in trying to squeeze money out of them at any cost, and he spent lots of effort and time investigating revolutionary technologies, some of which were so ahead of his time that he couldn’t convince anyone to invest on them, others which were really bordering on the delusional. In the end, he died mostly alone, poor and regarded by the establishment as some sort of eccentric mad scientist.

The same setup with the lights on

Now, back to the Tesla coil. In the setup above, we have a huge coil that is able to make sparks fly through regular air, and in this case also with a relatively large current. However, if we decrease the density of the medium, it’s easier to send sparks through it. This is what happens in a plasma globe, such as the one I pictured below, which is powered by standard AA batteries.

Straight from the 1980′s

4 Responses to “Tesla Coils”

  1. Caroline says:

    Maybe you were a Physics teacher in another lifetime? :)
    Tesla and Edison… now that’s a sore spot. In my opinion, Edison “ripped off” Tesla’s ideas and passed them off as his own, never giving poor Tesla the recognition he deserved. By the way, the town of Edison, New Jersey used to be called “Menlo Park, NJ”. The name was changed in honor of Thomas Edison to “Edison, NJ” since that is where he did his experiments. Actually, I attended a talk at the “Thomas Edison Innovation Foundation” center in Newark. It was a GE giving a presentation on the use of “clean energy”. It was rather odd walking into what looked like a shrine / temple to Thomas Edison – “the greatest inventor” I beg to differ.
    Edison, interestingly enough, was good friends with Henry Ford. They were both remarkable businessmen.
    I don’t know much else about the history of science between Tesla and Edison. Maybe an expert “historian of science” (and physics teacher in the southern hemisphere) can help us with some history of how Tesla came up with his ideas (and how Edison stole them)? :)

    • Hi Carol,

      Well, in something which can be probably be called another lifetime a long time ago in a galaxy far away I *did* briefly teach physics – at my old high school, doing demonstrations in the lab.

      As for the Edison township, well, I can see it from my window – it’s a few blocks away. :-) And yes, Edison does seem to be a superstar in New Jersey. :-) I don’t know exactly how much of Tesla’s ideas were stolen by Edison, but overall Tesla *certainly* did not get nearly as much recognition (both in terms of prestige and money) and he deserved. Edison’s popularity on the other hand was at least as much due to relentless self-promotion and aggressive business tactics as they were due to hard scientific work and ingenuity.

      Reading one of the many books about Tesla and his work and his ideas (such as this one : http://www.amazon.com/Tesla-Man-Time-Margaret-Cheney/dp/0743215362/ ) is certainly on my list.


  2. Carol Linden says:

    When I was a kid back in the 80′s (yep, I *did* was a kid by then ;-) ) I wanted soooooo badly a plasma globe like the one you showed… lots of arguments with my father in Radio Shacks about why it was such a bad idea to buy one and bring it to Brazil… :-)

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