why do tesla coils need spark gaps?

Question

just wondering

Answer 1

Before there were electronic oscillators--i.e., those which switch current on and off at radio frequency rates with tubes or transistors--the only way to get a high-frequency current was to create an electric arc in the air or other gas separating two electrodes. The current in such an arc changes rapidly and often, albeit randomly, producing a large signal filled with different frequencies. This is run through an L-C filter of some sort and then applied to the primary of the Tesla coil. It's pretty crude, but it works well enough, and the spark-gap was the standard means of obtaining large rf currents for many years. It was, however, a great day when power-handling electronic devices became reliable enough to get rid of the spark-gap transmitters.

Note that a Tesla coil is an air-core high-frequency transformer with an odd construction and a high turns ratio. It's far easier to discuss when you think of it that way.

Answer 2

I don't believe they need spark gaps to operate. The question is "what on earth are you going to do with this high voltage and high frequency source". Obviously, its principal use of for physics demos so enter spark gaps and their friends. There are a bunch of "Mr. Science" things you can do with Tesla coils.

Answer 3

The spark gaps are used in concert with capacitors to generate the high frequencies required to drive these coils. In these circuits the electrons bounce back and forth at the gap.