RE: Gap Question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Luke" <Bluu-at-cox-dot-net> 

It was mentioned that a spark gaps voltage will stabilize at a
particular voltage and the current and resistance will change.  I
understand that but it raises another question.

The amount of current through the arc will determine the cross sectional
area of the arc and therefore the resistance.

But what determines at what value the voltage drop across an arc will
stabilize at?

This is not in reference to a spark gap where the energy level is fading
but with a power source that is constant.

Luke Galyan
Bluu-at-cox-dot-net
http://members.cox-dot-net/bluu





Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net>

Hi Luke,

[LG>] Sniped portion of reply
The resistance of an unconfined arc will tend to decrease as you
increase
current since the conductive channel becomes fatter. The effective
resistance of the arc no longer a constant, but instead is a function of

the applied current. The voltage drop across an arc that bridges a fixed

gap length rapidly stabilizes to a comparatively low steady state
"burning
arc" voltage (~20 volts to ~150 volts depending on the electrode
materials).

As you indicate, the overall resistance of the arc is always positive.
However, an arc has a "negative resistance characteristic" since an
increase in current causes a rapid DECREASE in the arc's resistance such

that the arc's voltage drop tries to approach the burning arc voltage
for
the gap.


Best regards,

-- Bert --