Re: an experiment with di

Tesla List wrote:
> >From alan.jones-at-kaboodle-dot-comSun Jul 21 09:57:56 1996
> Date: Sat, 20 Jul 1996 22:22:00 GMT
> From: Alan Jones <alan.jones-at-kaboodle-dot-com>
> To: Tesla <tesla-at-pupman-dot-com>
> Subject: an experiment with di
> Richard Hull said:
>  > You would be amazed at how many people actually believe that the
>  > charge  is held in or on the plates of a capacitor!  The plates are
>  > only a way to
>  > apply a gradient to the dielectric and to drain it.  The charge is
>  > always retained 100% within the dielectric!  The plates are rather
>  > superfluous and not required.  They incapable of storing energy
>  > except as  an isotropic capacitance in air or free space where these
>  > media (k=1)are  the dielectric.
>  >
>  > I would be glad to discuss this matter further, if you wish.
>  >
>  >
>  > Richard Hull, Tesla Coil Builders of Richmond
> I just watched your video #52 where the gentleman was showing charging
> a cap and then taking it apart and putting it back together again. Why
> didn't it discharge when he handled it? If he had touched both plates
> at the same time he would have received a nasty shock and we would all
> have had a chuckle at his jumping around, after seeing that he was
> alright, of course.
> But he handled all three pieces of the cap including the dielectric
> and didn't get any shock. Yet after putting the cap back together, he
> drew a spark by shorting the plates. If the charge is held in the
> dielectric, then why didn't it discharge when he picked it up. He
> handled both sides of the plastic and skin is conductive, so what
> gives? And would there have been a discharge if he had just touched
> the jumper wire to each side of the plastic without it being
> sandwiched between the plates?
> I wish I had a piece of plastic laying around, I would try this
> experiment and see. Knowing my luck, I would get zapped <g>.
> Alan
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Alan, All

You are both correct and incorrect.  Handling the dielectric does 
discharge it provided you touch both sides.  If you pay attention, he 
used his finger tips.  This will only "locally" discharge the dielectric. 
(tiny surface area) He received no noticable shock.  I have done this a 
number of times, too.  I do not recommend this!!!!  He used mylar, the 
best plastic for this demo.  Also he immediately rolled it up into a 
tube.  This is the safest way to handle the charged dielectric.  A wire 
shorting the dielectric would only discharge the tiny area of its own 
cross section, not the entire sheet.  This is easily verfied with 
experiment.  This is not a battery and only that part of the dielectric 
incontact with matching, opposite sided conductive surfaces can discharge 
the dielectric and then, only in that one area.  Current will not pour in 
from other areas of the dielectric.  Most Tesla coilers are very weak in 
the understanding of electrostatics and the operation and inner workings 
of capacitors.  Actually, most physicists are too! 

 The average dry, non-sweaty, human being is about 100k ohms finger tip 
to finger tip. Therefore, no significant finger tip current will flow 
that will be noticable due to the tiny capacitance represented by the 
finger tips on both sides of the mylar sheet ( a few pf).  I would not 
mash my hands between the sheet though (chest currents)! 

 A very bad item to use for a dielectric would be the core or slug from a 
door knob cap!  This is a material of ultra high permittivity (barium or 
strontium titanate)  These are all two plate caps and the finger tips 
would be an invitation to a horrible shock as hundreds or even thousands 
of pf would exist in the small area of the fingers.  

Again I would not recommend this experiment to any one!  It is dangerous 
and only an experineced person who understands the physics of the 
scenario should even attempt it.  The only reason it was included on my 
tape is to prove to all that the charge held within a capacitor is 
totally held within the dielectric only!!!!  It has nothing to do with 
the metallic plates at all.

Richard Hull, TCBOR