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Re: [TCML] TC Newbie

Hi,

fully concur with Gary Lau about plastic bottle capacitors. Plastics
degrade from corona much more than inorganic dielectrica i.e. glass. Apart
from pucture strength, dielectric constant often is not even mentioned: If
i.e. PP(polypropylene) is compared to window glass, we have dielectric
constants:

     Poplypropylene  epsilon = 2.2...2.3
     Window glass            = 7.6...8
     Pyrex glass             = 4.8

     Remember: dielectric constant  multiplies  the capacitance per unit
surface. So for a window glass dielectric bottle cap vs. a PP bottle cap,
you get about 3.5 times more capacitance for an equal bottle.

Regards, Kurt
Basel, Switzerland

Lau, Gary wrote:

PETA is a very lossy dielectric.  But even beyond that, I think that
plastic bottles are not a good choice for bottle caps.  Any time
there is corona, visible or not, that will rapidly degrade and melt a
plastic dielectric and result in a puncture, and that is true
regardless of whether or not the plastic is a lossy dielectric. Glass is much more resistant to corona than plastic, so glass bottle 
caps can survive even with corona.  Corona is the reason that
commercial plastic dielectric HV caps are constructed as many lower
voltage units in series - so that the voltage across each section
will be below the "corona inception voltage". 
Regards, Gary Lau
MA, USA


-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On
Behalf Of Jim Mora
Sent: Saturday, December 06, 2008 1:25 AM
To: 'Tesla Coil Mailing List'
Subject: RE: [TCML] TC Newbie

Hello,

I wonder if 1 or 2 liter PETE coke (or whatever) clear plastic
bottles could be used. PETE has a very high dielectric strength and
puncture resistance and is thin enough to really raise the
capacitance and lower the weight a bit. Maybe PE bottles which are
thicker though. 
Jim Mora


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