Re: Gap Question

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

Original poster: "Hydrogen18" <hydrogen18-at-hydrogen18-dot-com> 

Actually, for the same reason it will cut sheet steel, if you pull the rod
out from the workpiece it will cause and undercut but still lay a (weak)
bead. You do not retract the rod but a gap still exists because the metal is
being heated and liquified very fast. This is why the welding rod will stick
under too low of heat. You are correct in the plasma statement, the welding
arc voltage of 35 volts should not jump an inch gap, but any welder will
tell you it can.

---Eric
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Wednesday, February 25, 2004 12:23 PM
Subject: Re: Gap Question


 > Original poster: robert & june heidlebaugh <rheidlebaugh-at-desertgate-dot-com>
 >
 > Luke: In an arc you have several conditions to consider. 1) With a low
 > current arc the insulation value of the gap breaks down forming a small
 > current path. this small current , path MAY MOVE ALONG THE CONDUCTOR BY
 > THERMAL AGGITATION, but remains a small current path. 2) At high current
 > another conditions takes place forming a plasma. A plasma forms when the
 > energy of the arc strips the outer shell of electrons off the atoms of the
 > conducting gas. At this point the plasma becomes a conductive path of a
 > large area with very low resistance. A gap 2 " in distance can freely
 > conduct 28 volts. At normal conditions 28 volts could never be conducted
 > across a 2" gap. In a TC we are not using low current pulses we are using
 > current pulses over 200 amps. An example of this action is an arc welder .
 > The tech moves the arc rod close to the base metal to strike the arc then
 > holds the arc some distance away from the base metal plate to heat a
larger
 > area and form a metal puddel for welding. If the tech moves the arc to
farr
 > a large round hole will form , not a single small point hole. This action
is
 > used to scrap out sheet metal in junk yards with an arc welder set on high
 > currernt a 1" wide strip can be cut in old scrap for much less cost and
time
 > than using an expensive cutting torch. 3) The plasma action can be proven
in
 > several ways,  The primary proof is the sudden drop of resistance of a
gas.
 > this the reason flourecent lamps have a balest coil in the circuit. The
 > filament heats the lamp to forn a conductive vapor then the lamp conducts
 > and the resistance drops. The balest then provides reactance to limit the
 > current of the gas in the tube and you get light across the entire
diameter
 > of the tube not just one thin line of arc.  Another example is found in
 > inert gasses. These gasses will not form compounds and are called NOBLE
 > gasses. In a plasma inert gas will react with chlorine or fluorine to make
a
 > stable salt compounds such as zenon chloride which you can buy from a
major
 > chemical supply.
 >     Robert   H
 > --
 >
 >
 >  > From: "Tesla list" <tesla-at-pupman-dot-com>
 >  > Date: Wed, 25 Feb 2004 07:24:57 -0700
 >  > To: tesla-at-pupman-dot-com
 >  > Subject: RE: Gap Question
 >  > Resent-From: tesla-at-pupman-dot-com
 >  > Resent-Date: Wed, 25 Feb 2004 07:38:12 -0700
 >  >
 >  > Original poster: "Luke" <Bluu-at-cox-dot-net>
 >  >
 >  > Sorry, when I wrote gap in this post I should have said arc.
 >  > So when the term negative resistance is used what is meant is that the
 >  > resistance value is changing in a negative direction (getting less)?
 >  > Is that a correct statement?
 >  >
 >  > An actual resistance value that could be measured in the negative is
the
 >  > picture the words negative resistance brings to my mind (sort of).
Just
 >  > seems like a misleading term at lest to someone new to this concept
like
 >  > me.
 >  >
 >  > 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 5:19 PM
 >  > To: tesla-at-pupman-dot-com
 >  > Subject: RE: Gap Question
 >  >
 >  > Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz>
 >  >
 >  > On 24 Feb 2004, at 13:09, Tesla list wrote:
 >  >
 >  >> Original poster: "Luke" <Bluu-at-cox-dot-net>
 >  >>
 >  >> So if the current goes up the gap widens.
 >  >
 >  > The arc channel increases in diameter.
 >  >
 >  >> If the gap widens the resistance of the gap goes down.
 >  >
 >  > If the arc channel increases in diameter, the resistance of the gap
 >  > goes down (assuming the arc length remains constant).
 >  >
 >  >> If the resistance went down when the current went up
 >  >> That is resistance not negative resistance.
 >  >
 >  > No. With a "normal" resistance, as current through the resistance
 >  > goes up, the voltage across it goes up and vice-versa. In the case of
 >msnip........