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RE: Dielectric Constant?
The dielectric constant of the oil in a home-made rolled or flat plate poly
cap is irrelevant. It is the dielectric constant and dissipation factors of
the plastic separating the aluminum plates which determines it's capacitance
and lossiness. The oil is used just to displace air bubbles which would
otherwise form corona and damage the poly. While oil does have a dielectric
constant, it won't affect the properties of the capacitor unless the oil is
the only thing between the plates.
What you want in oil is for it to be thin - low viscosity, so that it fills
all of the nooks and crannies between the foil and plastic, although this is
difficult to do well unless you draw a vacuum before backfilling with oil.
Motor oil is made to be thick and viscous. Instead, use mineral oil from
the laxative section of any drug store. It also is easier to dispose of
after your cap ultimately blows (and it will!), as laxative-grade mineral
oil is made to be flushable.
Regards, Gary Lau
Waltham, MA USA
From: Tesla List [mailto:tesla-at-pupman-dot-com]
Sent: Sunday, June 04, 2000 2:06 AM
Subject: Dielectric Constant?
Original Poster: "Arthur Mavros" <mpiece-at-one-dot-net.au>
does anyone know the dielectric constant for 'car
engine oil' and its
puncture rate? Is it usable for a basic plate cap?