Re: Graphite spark gaps (fwd)
---------- Forwarded message ----------
Date: Thu, 30 Apr 1998 11:05:06 +1200
From: Malcolm Watts <MALCOLM-at-directorate.wnp.ac.nz>
To: Tesla List <tesla-at-pupman-dot-com>
Subject: Re: Graphite spark gaps (fwd)
> Date: Wed, 29 Apr 1998 09:22:02 -0400
> From: Aric C Rothman <Aric_C_Rothman-at-email.whirlpool-dot-com>
> To: Tesla List <tesla-at-pupman-dot-com>
> Subject: Graphite spark gaps
> Has anyone had success using graphite electrodes in a static spark
> I've built one using hexagonal pieces of artist's graphite (approx.
> 1/2 inch across, 6B grade (alot of C, little binder)). I tried it out
> by connecting it across the series-connected secondaries of two
> microwave transformers. It produced a fierce, bright spark. The
> spark was so hot it ignited the wood base of the spark gap assembly.
> I've read that graphite has a negative temperature coefficient (as it
> gets hotter, its resistance goes down). This property would appear to
> make it a great choice for static spark gap material. Other than the
> mechanical problems associated with using graphite (fragile, can't be
> soldered or welded), are there any reasons why graphite would be a bad
> choice for Tesla coil use?
The negative resistance characteristic is an inherent property of
sparks (ionized matter). Graphite is a terrible choice. It is
designed to ablate, it has more resistance than copper etc and you
can see the power being lost in the gap :( The ideal gap issues no
light, no heat and no sound, just conducts as though it wasn't there.