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Re: [TCML] Voltage - Flame



On 1/28/12 7:27 AM, James Zimmerschied wrote:

That being said, the discussions did bring up some interesting
points:1) there does not appear to be a reliable way to determine the
voltage a coil has to produce to create a given spark length. If
there was someone could have pointed to the data.

That's because there isn't a particular "voltage" that's needed to create a given spark length. The Jacob's Ladder example is a good one, because you can create a very long spark with fairly small initial voltage. That's the classic "drawn arc" kind of situation.

ALl you can really say is that the voltage has to be high enough to start the spark growing, and that just means that the voltage has to be high enough that the field locally exceeds 3MV/meter.

That said, I think that there is a practical relationship: Say you had a 2 cm diameter top load. You could start breakout at 30kV (or less, if it had a sharp point on it), but such a terminal doesn't have the charge storage capability to keep the spark growing.



2) the theoretical
voltage on the top terminal is stated to be dependent on the radius
of curvature of the top load  - however spherical top loads do not
produce the longest sparks.

Precisely so.


 3) Other types of coils use a breakout
point (DRSSTC, VTTC). The DRSSTC seems able to create very long
sparks with this small radius of curvature point at the top load. I
think it is a good idea to find a reasonable and accurate way to
measure the voltage at the top load of a Tesla coil and then if
enough folks make the measurement with different coils it may be
possible to say that "on average" these type coils produce x voltage
at the top terminal when producing y spark length.

I think it's more complex than that. It's about supplying charge to a growing spark channel, and that depends on the inductance & capacitance of the terminal, more than the actual voltage.

because there is a coupling between amount of charge and voltage & capacitance, and the latter is related to size, that's why one can probably say

Bigger sparks require higher voltages on the TC topload

but you also have to say

But spark length depends on a lot of other factors.


You certainly can't boil it down to a distance per volt sort of metric.

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