Re: water spark gaps

["Tesla list" <tesla-at-xxxxxxxxxx>]

Original poster: "Gary Johnson" <gjohnson-at-ksu.edu> 

I have made underwater sparks.  Never thought about it as possibly being
useful in Tesla coil work until Terry asked the question.  Maybe I lack
imagination, but I doubt that it will catch on like the MMC has.  But let me
briefly tell of my observations.

I charged a 2 microfarad capacitor to voltages between 1 and 10 kV, and
discharged the capacitor to a small amount of water inside a piece of
plastic tubing through a 38 microhenry inductor.  At voltages up to about 6
kV, the water acted as a relatively high resistance and the circuit decayed
as an overdamped RLC circuit.  Resistance decreased with time.  When the
resistance dropped below about 10 ohm, the water would explode if the
capacitor still had sufficient energy.

During the explosion, resistance would drop still more, so the circuit would
become underdamped and oscillatory.  Remaining water droplets were cool to
the touch, so there is no evidence that the water had boiled into steam.
Some explosions were followed by a low impedance arc in air, so what was
happening in water was distinctly different from what was happening in air.

The size of the explosion was surprising to me.  A few drops of water would
sound like a 12 gauge shotgun.  Tap  water or saturated salt water made no
difference.  Distilled water was more difficult to explode.

The main researcher on this topic is Peter Graneau along with his son Neal.
If anyone is interested, email me off-list and I will send you a list of his
papers.

Gary Johnson


At 09:26 PM 11/28/2000 -0700, you wrote:
>Original poster: Terry Fritz <twftesla-at-uswest-dot-net>
>
>Hi All,
>
>	Has anyone ever experimented with water spark gaps?  If so, did you run
>into any big problems? 
>
>Cheers,
>
>	Terry
>
>