RE: Gap Question

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

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

Antonio:
Is it that the negative slope of the V I curve occurs from when the gap
first breaks down until the voltage across the gap has dropped?

So if the arc were looked at as an arc that has already broken down the
V I curve would be the normal slope you would see with a resistor if
voltage supplied to it were varied?

But the act of breaking down is like changing the gap area from an
infinite resistance into a lower resistance and that is when this
negative resistance characteristic takes place?








Side note and question:
With positive resistance the current will drop when the voltage across
it drops.
With negative resistance the current will rise when the voltage across
it drops.
This is the concept of negative resistance right?

Doesn't a normal switch display negative resistance?
With the switch open the voltage across it is high and the current is
low.
With the switch closed the voltage across it is low but the current
through it would be high (assuming there is a load present).
So with a switch when the voltage dropped the current went up.  That is
the opposite of what a resistor would do.

But since we are used to looking at standard electronic components
(caps, res, ind, diode, etc.) we try to compare it to what we know, and
it looks most like a resistor but backwards so we dub the term negative
resistance?

So is it really that there is negative resistance or is it a change of
state kind of thing that is displayed?  Are we just calling a change of
state negative resistnace?

Sort of like trying to freeze water.  You can start cooling water down
and it will drop in temperature linearly down to about 32 degrees f.
once at that temp you need to keep pulling more and more heat out of it
to get it to turn to ice.  But while pulling out this heat the
temperature never dropped. All the heat removed left the temp the same
but made the water solid (change of state).  If we did not know how the
change of state verses btu's thing worked with water we would be a bit
stymied as to what was happening.  Not sure what we would try to call it
but you get the drift..........
Ignore this last paragraph if you think I am rambling.  :)


Thanx

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: Monday, February 23, 2004 10:50 AM
To: tesla-at-pupman-dot-com
Subject: Re: Gap Question

Original poster: "Antonio Carlos M. de Queiroz" <acmq-at-compuland-dot-com.br>

Tesla list wrote:

  > Original poster: "Luke" <Bluu-at-cox-dot-net>
  >
  > Holly cow that did throw a bit of a wrench in there.  My gears just
  > stopped.  That is hard to conceptualize based on im so used to the
ohms
  > law concept being so natural to me that it is very hard to imagine a
  > negative resistance.  Not sure how to go about wrapping my head
around
  > that one.

The negative resistance characteristic appears in any device that can
first sustain a high voltage without conduction and then suddenly
starts to conduct, while the voltage drops. The current x voltage
characteristic is something as:

|i      *
|     *
|   *
| *
| *
|  **
|    **
|      *    v
+******------

There is a region where the inclination of the curve is negative.
This happens in spark gaps, gas-discharge lamps, pnpn diodes, etc.
The curve is similar, reflected, for negative voltage and current.
Note that the negative (incremental) resistance doesn't last for
any value of current, and that the power dissipated in the element
is always positive.

Antonio Carlos M. de Queiroz