Re: Final Preparations fo Tesla HD Project, Questions

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

Original poster: "Terry Fritz" <twftesla-at-uswest-dot-net>

Hi Josh,

At 12:12 AM 2/27/2001 -0500, you wrote: 
>
> Fellow Tesla Enthusiasts, 
>
> Being that the regional competition for National History Day is this weekend,
>
> I felt that I should ask a question that's been bothering me for a while 
> (moreso these past few hours, I discovered something...). 
>
> A couple hours ago, I noticed that an interesting "force-field" effect can be
>
> produced with the 15,000 V 60 mA NST i'm going to use for a Jacob's Ladder 
> for the exhibit on Tesla for HD (the title of my exhibit is "Nikola Tesla - 
> The Legacy of Alternating Current"). I was experimenting with a length of 15 
> kV rated wire attached to one terminal of the NST when I discovered that a 
> weird sensation can be felt when moving my hand over the surface of the 
> insulation. It is really weird though as it reminds me of a force field 
> surrounding the wire. About an inch away I can feel a buzzing electrical 
> feeling in my hand, similar to static, only constant, more powerful, and it 
> somewhat restricts the movement of my hand the closer it gets to the surface 
> of the insulation. 


That is current passing to your hand much like a static charge.  The insulation
stops DC current from flowing but a little AC current is getting through since
the insulation on the wire is acting like the dielectric in a capacitor.  The
wire on the inside and your hand are the terminals and the insulation is the
dielectric.  At 15kV the current is very noticeable and that is what you feel. 
Be a bit careful that there are no breaks in the insulation or it could arc
through directly to hour hand!



>
> I've hypothesised that this is a capacitive effect; the wire and my hand 
> being the plates of the virtual capacitor and the insulation being the 
> dielectric. Further evidence that supports this conclusion is that the 
> sensation intensifies as more of my hand is exposed to the wire. 


Oops!  You already figured it out :-))


>
> So my main concern is: will it be a problem when running the Jacob's Ladder 
> around many people? I have only tried it with the wire connected to one 
> terminal, and not arcing to the opposite terminal or ground, and yet the 
> sensation was quite strong. Will this "force-field" become a problem with the
>
> full 900 VA flowing through the wires, possibly presenting a shock or fire 
> hazard? 


No.  The current only flows significantly if there is a grounded object
practically right next to the wire.  The ladder will create radio interference
that may affect nearby cell phones and radios but nothing to serious.  There is
a tiny chance it could affect a pacemaker but no one will get that close to it
when it is running anyway.  You may mention a little warning about pacemakers
and RFI.  Pacemaker wearers already know to avoid such odd electrical
contraptions from their doctors but you may mention it.


>
> I've already planned out everything i'm going to do to prevent mishaps during
>
> the competition, such as a crude lockout mechanism (it won't work without the
>
> fuse ;-)), HV wire, insulated terminals, etc. Plus, i'm not planning on 
> leaving the HV stuff anytime during the competition. The Jacob's Ladder will 
> also be run with a fairly low duty cycle (5 seconds on, 30 off) to reduce 
> electrode heating. 


You should be sure to always stay with it while its running.  Especially with
kids and such around since you never know what might happen.  It really needs
someone right there to watch over it.


>
> Also, if any of the list members would be so kind as to let me interview them
>
> (telephone, online, etc.), I would be eternally grateful. Contact me off list
>
> and we may be able to work something out. Thanx!!! I would also like to thank
>
> those that have already helped me with this project, I really appreciate it. 


I'll send you my number since long distance is fairly cheap for us ;-)


>
> Regards, 
>
> Josh Hunsaker 
> ---------------------- 
> Denver, Colorado 
> ArcStarter3-at-aol-dot-com