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Re: Elementary Lecture

   Why sparks will leap between the toroid and a grounded object is quite
understandable; but the magic of a Tesla coil is that sparks spontaneously
branch
out into thin air, connecting with seemingly nothing.
   Consider 2 devices: A million volt Tesla Coil, and a million volt 60 Hz
transformer. The TC will emit a discharge into the air that connects to
nothing.
We'll help the million volt xfmr by grounding one of the secondary HV
terminals.
Do sparks spontaneously emanate from the other HV terminal into thin air? No.
   I certainly have not read all available Tesla coil theory, but I've yet
to see
a thorough explanation of why a Tesla Coil does what no other device can
do--emit
sparks that terminate in the air.
Dave Hartwick

Tesla List wrote:

> Original Poster: Jim Lux <jimlux-at-jpl.nasa.gov>
>
> Tesla List wrote:
> >
> > Original Poster: Brandywine <brandywine-at-writeme-dot-com>
> >
> > If anybody has a good adult coiler answer to "why sparks come off the
top",
> > I'd be interested.
>
> Assuming you mean why do they come off the toroid/top load: The voltage
> is highest there, relative to ground (or the surroundings), and the
> radius of curvature is tightest, so the electric field (volts/meter) is
> highest. Wherever the field is highest, it breaks down first.
>
> If you put a grounded (or suitable metal) object near the coil, you can
> distort the field, causing the highest field to occur somewhere else,
> and the sparks will break out there. For instance, if you attach a short
> length of copper tubing (about 6" long) on the end of a long piece of
> PVC pipe (or some other LONG insulated handle), you can move it around
> your coil and hold it in different orientations to see what happens. If
> the axis of the tubing is crossways to a line from the coil to the
> tubing, it won't have as much effect as if the axis is parallel.
>
> A grounded wire works even better, actually "attracting" the sparks to
> it (much like a sharp pointy lightning rod works by increasing the field
> near the rod, making the strike probability higher there, as opposed to
> the smoothly curved surface of the top of your head, for instance)
>
> Now, as to why the sparks go up from the top.... THis is a bit more
> iffy, but I'll bet it is because sparks are hot, and hot air rises.
>
> --
> Jim Lux                               Jet Propulsion Laboratory
> ofc: 818/354-2075     114-B16         Mail Stop 161-213
> lab: 818/354-2954     161-110         4800 Oak Grove Drive
> fax: 818/393-6875                     Pasadena CA 91109