Re: DC/AC sparks

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-qwest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "davep by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<davep-at-quik-dot-com>

>         Perhaps.
>         Max voltage depends on (among other things) drive voltage AND
>         leakage from terminal.  Toroid minimizes leakage.

Not in a Marx generator. A terminal there serves only as a guarantee
that the output energy will go to where you want it, and not to
where it wants to go due to sharp points in the output area.

>         Or....
>         Even if the charge voltage is an arbitrarily symmetrical wave
>         form, be it undamped, or damped, a DC component can appear
>         IF the top terminal, by shape, causes partial rectification.

This can't last for long time. Any DC at the terminal would cause an
increasing DC current through the -grounded- secondary coil, that would
drain it very fast. At long term, the average voltage at the terminal
must be zero, no matter what kind of nonlinearity is caused by sparks.
 
>         cf above.
>         And a number of people report residual charges, consistent
>         with DC from 'somewhere'.

Charges accumulated at the insulated surface of the secondary coil,
-never- at the terminal.
 
>         It is well documented, that, for any terminal (and especially
>         a sharp one) the max voltage achievable (or the leakage from,
>         which is the same) VARIES WITH POLARITY.

Certainly. Negative charges leak more easily.
 
>         It has been widely reported, for varying designs, that there is.
>         It appears to be on the order of a few KV, rather than the
>         100s of KV associated with the nominal output, however the
>         DC does seem to be there.

Rectification by sparks can cause a DC component in the current 
trough the secondary coil, never a DC voltage at the terminal if
the secondary coil resistance is insignificant. Ok
that this DC current can produce a resistive voltage drop along
the secondary, and this drop can be measurable. But not of KV.
 
>         A small (on the 100s KV scale) DC offset is easy to miss.

??

>         Streamers can be nicely made by AC.

They surely can.

>         (DC measurements at the base would be intriguing, even instructive.
>         Also challenging...)

Some experimenters have inserted a big capacitor between the secondary
base and the ground, and found that it is quickly charged to a high
voltage when the coil operates. 

Antonio Carlos M. de Queiroz