Re: Dielectric absorption (was LED Charge Indicator)

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Peter Terren" <pterren@xxxxxxxxxxxx>

Triboelectric static generation is how van der Graaff generators work 
of course.  I actually suspect that they are just manifestations of 
the same effect.  I conceptualise it as moving two charged plates 
away from the dielectric and the voltage increases as capacitance 
decreases to conserve stored energy of 1/2CV^2.  The dielectric has 
'absorbed' the charge as a low voltage stress in the molecular 
structure to allow this to happen.

Peter


> Original poster: dave pierson <davep@xxxxxxxx>
>
> >Dielectric absorption was demonstrated dramatically when I unrolled a
> > defibrillation capacitor (36uF 5kV) and sparks were developing giving
> > me little shocks.  Tearing the dielectric and film/foil gave rows of > tiny
> > sparks captured with my digital SLR camera.
>    Is this _dielectric absorption_, or a mutant form of  'frictional' static
>    electricity.
>
>    Once upon a time, when film was used in cameras (8)>>), disassembling
>    the film for processing in a DARK room led to sparklies (I assume it
>    still does.....)
>
>    (OK:
>    I may be being pedantic, but was involved in 'real' dielectric
>    absorption measurements in instrumentation, when getting
>    started.  by definition this was a residual charge that did not
>    leave the cap immediately...  Occurs in all dielectrics, usually
>    too small to be noticable....)
>
>    best
>       dwp