Re: Elementary Lecture

To: tesla-at-pupman-dot-com
Subject: Re: Elementary Lecture
From: Dan Kline <ntesla-at-ntesla.csd.sc.edu> (by way of Terry Fritz <twf-at-verinet-dot-com>)
Date: Thu, 25 Feb 1999 11:42:10 -0700
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>Date: Wed, 24 Feb 1999 16:08:51 -0700
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>Subject: Re: Elementary Lecture
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>Original Poster: Brandywine <brandywine-at-writeme-dot-com> 
>
>   Why sparks will leap between the toroid and a grounded object is quite
>understandable; but the magic of a Tesla coil is that sparks spontaneously
>branch
>out into thin air, connecting with seemingly nothing.
>   Consider 2 devices: A million volt Tesla Coil, and a million volt 60 Hz
>transformer. The TC will emit a discharge into the air that connects to
>nothing.
>We'll help the million volt xfmr by grounding one of the secondary HV
>terminals.
>Do sparks spontaneously emanate from the other HV terminal into thin air? No.
>   I certainly have not read all available Tesla coil theory, but I've yet
>to see
>a thorough explanation of why a Tesla Coil does what no other device can
>do--emit
>sparks that terminate in the air.
>Dave Hartwick

I'd bet it's capacitive breakdown. For example, there's a plasma-globe, and
then there's a Tesla-coil. The plasma-globe arc-fingers are heading towards
the highest capacitance found, i.e. the outer glass globe, or where your
finger is on the globe. The Tesla-coil is probably doing the same, but
there's not enough energy to make an arc-finger that will reach to (as far
as the Tesla-coil is concerned) an "infinite" capacitance. The effect is
easily simulated in a plasma-globe with the power input lower than normal. 

The capacitance the Tesla-coil sees could also be the walls of your
building, objects around the room, etc. This might also explain why an arc
will sometimes directly bypass a good ground and hit some other object. I'd
guess that there's really no difference between the two effects, other than
that the Tesla-coil's "globe" is far, far away.
Dan