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Re: Elementary Lecture
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
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