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Re: [TCML] Spark dynamics on Jacobs Ladder
A simple explanation, understandable by elementary school kids, is this: A
wire carrying a current has an EM field around it. The two wires carrying
currents in opposite directions will thus attract each other. When the spark
first forms at the bottom, the two electrodes form effectively very short wires.
As the spark rises, their lengths becomes effectively longer and the
attraction stronger. The maximum attraction occurs when the spark is at the top.
When the spark breaks at this point, the restorative force of the spring tension
of the electrodes pulls them apart again and they try to oscillate at their
natural frequency. If you could get the voltage, current, spark travel time,
and distance just right, you would see significant resonant gain in the
movement (The pushing-a-swing analogy). The college-level explanation is here:
Hope this helps,
In a message dated 1/18/08 11:06:32 A.M. Eastern Standard Time,
I hope this isn't viewed as too off-topic - I'll argue that the same physics
apply to TC sparks ;-)
I was giving a demonstration of various HV toys to a 4th grade class
yesterday. Among the devices was a Jacobs ladder, powered by a 15/30 NST. The two
1/8" x 3 ft steel electrodes appeared to have been excited into a mechanical
oscillation, bouncing towards and away from each other, at very roughly ~
1Hz. One of the students asked my why they were moving, and I had to admit that
I didn't know the source of the force that was moving them.
The period of the oscillation was much faster than the arc travel time up
the electrodes. It's clear that the period was that of the free-standing rods,
and that the exciting force between them varies as a function of their
separation, but I don't see the source of the attraction or repulsion between
them. Any theories?
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