Wet Coils

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

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Terry,

>Did you ever try a coil that was wet or maybe even underwater to see if
inductance would change?  That woudl be sort of interesting especially if it
did.  I'll search around here to see if I have a coil that can be soaked too
and try...

Oh Great!  Now we're going to do a swimsuit issue.  I'll do it right now.

OK, that didn't take long.  I checked the same coil as last night, it read
4.57mH before starting.  I placed the coil while connected to the LCR meter
on the floor of the shower and turned on the water.  Some water droplets
coated the outside of the coil.  After two minutes the inductance was still
4.57mH.  So I wrapped a soaking wet towel around the coil and measured the
inductance.  After a couple minutes the inductance did appear to increase
just enough that the reading vacillated continuously between 4.57mH and
4.58mH.  It did appear to change the inductance measurement somewhere
between 10 to 90 nanohenries.  That's the best resolution I have at this
range of inductance.

Mind you, this is with a wet towel.  Not only is the humidity 100%, but
there is a substantial mass of water in close proximity to the windings.
Tomorrow I'll get a bucket and actually submerge the coil and see what
results I get.

>I think the inductance is stable but water in the woodwork and such is
affecting the capacitance of the secondary a little causing the variation in
frequency.

Do you have an ion generator?  If so, put it next to the coil and see what
you get.  If you don't, they sell them at All Electronics for less that $5
each.  It's really a useful device to have on hand when working with some
electrostatics projects.

>Paul can predict by computer that a lot of the Q variation is due to copper
resistance changing with temperature

Has this prediction been verified by manually heating the coil with
something like a hair dryer?

>but surrounding humidity in the house woodwork is having an effect too.
Rain on the roof has a dramatic effect!!  Note that the variation is only
0.1%  What does have us stumped is the q of f1 stays stable but f3 and
especially f5 vary a lot.

What exactly are the parameters of f1, f3, and f5?  I wondered that when
looking at the graphs.  You wanted someone to peer review your project, I'm
interested in fully understanding your results.

As for the rain on the roof, did you consider the effect of falling water
producing ions?  When I placed ions next to my coil, the inductance
measurement changed considerably.  When I placed water next to the coil
there was barely an effect at all.  You may be misinterpreting the mechanics
of the weather.

>I must write up the details or the data will be just as sketchy as
Tesla's...

We don't want that.  Let's get to the bottom of this.  I now have a personal
interest in your data and results.

>I can just hear them 100 years from now "Yep!, Terry and Paul sure took
some great data there but to bad we don't know what of..."

LOL  Yes, but the way some people fear, our currency will say "In Tesla We
Trust"  and we will be doing prayers and prostrations before his image.  As
a canonized disciple of Tesla you will be loved and revered by all based
entirely on faith.  Praise be Tesla!

>A lot of detail is at:
>http://www.pupman-dot-com/listarchives/2002/April/msg00366.html

Cool!!!

Dave