RE: Gap Question

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi,

Negative resistance = As the current goes up, the voltage goes 
down.  Opposite a resistor.  Common light bulbs have negative 
resistance.  It "sounds" a lot more complex than it is ;-))

Cheers,

         Terry




At 05:48 PM 2/24/2004, you wrote:
>That put it into words that clicked with me.
>Thanx.
>
>And negative resistance characteristic is easier to swallow than
>negative resistance.
>
>Still mulling this over.
>
>Luke Galyan
>Bluu-at-cox-dot-net
>http://members.cox-dot-net/bluu
>
>-----Original Message-----
>From: Tesla list [mailto:tesla-at-pupman-dot-com]
>Sent: Tuesday, February 24, 2004 4:17 PM
>To: tesla-at-pupman-dot-com
>Subject: Re: Gap Question
>
>Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net>
>
>Tesla list wrote:
>
> >Original poster: "Luke" <Bluu-at-cox-dot-net>
> >So if the current goes up the gap widens.
> >If the gap widens the resistance of the gap goes down.
> >If the resistance went down when the current went up
> >That is resistance not negative resistance.
> >
> >Luke Galyan
> >Bluu-at-cox-dot-net
> >http://members.cox-dot-net/bluu
><SNIP>
>
>Hi Luke,
>
>In a normal resistor, the voltage drop increases linearly as you
>increase
>current since the resistance is a constant (not a function of current),
>so
>that doubling the current simply doubles the voltage drop. This is
>defined
>as positive resistance characteristic.
>
>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.
>
>Macroscopically, a spark gap can be envisioned as a pair of back to back
>
>Zener diodes with a 100-150 volt drop (Egap). Adding more gaps in series
>
>will add more discrete voltage drops into the primary LC circuit. Each
>additional spark gap adds an increment of loss (Iprimary*Egap), so
>multiple
>gaps will tend to be lossier than single gaps (all other things being
>the
>same). Multiple gaps often handle high power levels more effectively
>without needing to resort to a heroic level of forced air cooling.
>However,
>a well designed high velocity single-gap system (such as Gary Lau's
>vortex
>vacuum gap) will be more efficient than a multi-gap system assuming that
>
>they both style gaps are capable of quenching at the same primary
>current
>notch.
>
>Best regards,
>
>-- Bert --
>--
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