Re: Voltage determination

["Barton B. Anderson" <tesla123-at-pacbell-dot-net> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)]

Hi Jim, All, 

Agree about the needle and ROC situation, but I'm not sure about the 30kV/cm. I
have no idea what it is but I'm starting to wonder if this value varies. I've
seen this value used (and several others). In the archives, I read a 1998 post
from Bill Wysock stating that 13M "may" be around 8kv/inch (or near) and that
the output voltage was about 1/3 less than originally thought. This was based
on an IEEE paper he was reading at the time which appeared to leave an
impression on him. 

I'm not sure if Bill remembers that one, but it did start me pondering that
possibly a volts/unit value may change with coil power, dimensions,
environments, etc. If it does change, then is it too much to use a standard?
Maybe it doesn't - I don't know. 

I'm curious if anyone else has insight on the subject. Is there a consensus? 

Thanks, 
Bart 
  
  

Tesla list wrote: 
>
> Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov> 
>
> in free air, uniform field (not the case with a TC), it is roughly 30 
> kV/cm.  Needle gaps run about 1/3 that (or close to the 1 kV/mm from 
> Jeroen), but, OTOH, needle gaps are notoriously erratic, especially as the 
> voltage gets high.  They are particularly sensitive to surrounding objects 
> that perturb the field, and to various other ionization effects (UV, 
> radiation, etc.) 
>
> You could use the uniform field number as an upper bound.. 
>
> The voltage on a TC is more realistically limited by the radius of 
> curvature of the top load.  If your top load had a radius of curvature of 
> 10 cm (i.e. the "tube" of the toroid was 8 inches in diameter), and it were 
> very smooth, the maximum voltage would be around 300 kV. Any bumps, 
> ripples, etc. will tend to reduce the voltage.  The larger diameter (i.e. 
> across the toroid) has very little effect on the breakdown voltage, but a 
> lot of effect on the capacitance. 
>
> When the field is nonuniform (and changing), you can produce very long 
> sparks in a very low overall field.  The field before lightning strikes is 
> typically less than 10 kV/meter, and that's a fairly long spark in a field 
> that is 1/300th that for breakdown (3 MV/meter) 
>
> ---------- 
> > From: Tesla list <tesla-at-pupman-dot-com> 
> > To: tesla-at-pupman-dot-com 
> > Subject: Re: Voltage determination 
> > Date: Friday, July 21, 2000 4:32 PM 
> > 
> > Original poster: "J. Kooiman" <jkooi-at-wish-dot-net> 
> > 
> >  Hi Tom, 
> > 
> >  There is a standard to it, 1000 V (1kV) by 1 mm 
> >  So for 40 cm that would be around 400.000 Volts (400kV), give or take a 
> few. 
> > 
> >  greetings from Jeroen Kooiman from Holland. 
> >  web :
> <http://www.crosswinds-dot-net/~jeroenk>http://www.crosswinds-dot-net/~jeroenk 
> > 
> > 
> > 
> > 
> > > Original poster: "TruckDrivingMan" <Tom.Ansorg-at-t-online.de> 
> >  > 
> >  > Hi all ! 
> >  > I just finished my first coil,and I was wondering how much kVolts it 
> >  > spreads.The spark length is ~40 cm,the NST needs ~1,7 kW.Any ideas for 
> >  >  measure 
> >  > methods ? 
> >  > 
> >  > Tom 
> > 
> > 
> > 
> >