|This is the talk page for discussing improvements to the Spark gap article.|
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- 1 Cyan isn't blue?
- 2 Clarify the difference
- 3 Maxwell Forces
- 4 Gas Discharge Tube
- 5 New moving image
- 6 Any light emission hazards with Jacob's Ladder?
- 7 Circuit symbol
- 8 Fluorescing?
- 9 Length of HV arc
- 10 Jacobs Ladder
- 11 unusual devices?
- 12 Break up article?
- 13 Power-switching devices
Cyan isn't blue?
I don't consider it vandalism  to use the most familiar term; in a general sense, cyan is a shade of blue to most people, just as magenta or fuchsia might be considered pink (indeed, as the cyan article notes, cyan often goes undistinguished from light blue). To state in the article that cyan is not blue  implies that the reader's perceptions are wrong. I've rephrased to what I hope is an acceptable compromise, "cyan or blue." -- Wapcaplet 15:54, 30 Oct 2004 (UTC)
Clarify the difference
- Well, for sparks and arcs, I'd say "no difference". A corona discharge is clearly different, being a diffuse (dispersed) discharge rather than a single (or few) heavily ionized conduction channels.
- Atlant 13:57, 1 Jun 2005 (UTC)
Matl culled from page
I dont think this is correct;
However, the heated air is not what causes the arc to rise. The arc rises because of what is known from Maxwell's equations. Maxwell's equations state that a current through a normal magnetic field will cause a force on the current in the direction given by the right-hand rule. This force is what causes the arc to rise.
--Light current 04:10, 31 March 2006 (UTC)
- On 3/29 220.127.116.11 added the following:
- "However, the heated air is not what causes the arc to rise. The arc rises because of what is known from Maxwell's equations. Maxwell's equations state that a current through a normal magnetic field will cause a force on the current in the direction given by the right-hand rule. This force is what causes the arc to rise."
- I disagree. If the above were true, then, if the diverging pair of wires was inverted so that the narrowest portion was at the top, then the arc should travel downwards from the top. This is not observed (at least for low current high voltage arcs). Lorentz Forces acting upon the arc are directly proportional to arc current. In the case of the travelling arc, the typical arc current is usually less than an ampere. Although J x B forces do become significant for high current (kA or MA) arcs seen in railguns, HV circuit breakers, and high current spark gaps, for low current traveling arcs the upward movement is almost entirely due to rising hot air. Bert 04:28, 31 March 2006 (UTC)
- Thanks for the clarification. I'm sure you could tell that this is my first time getting into a disagreement on Wiki, and I was frustrated because I didn't know how to contact the person disagreeing with me. -David Drinnan
Just put your comments on the talk page. Editors will probably see them there!--Light current 08:43, 31 March 2006 (UTC)
Actually, the Maxwell force is not negligable, which can be shown by having a horizontal Jacob's ladder, such as http://www.flickr.com/photos/mightyohm/3584678636/ Mossig (talk) 14:14, 31 October 2013 (UTC)
- Spark = disambig links to spark gap and voltaic arc
- Arc = disambig links to voltaic arc and electric arc
- Voltaic arc --> redirects to electric arc
- Electrical discharge --> redirects to Electrostatic discharge
- Discharge = disambig links to electrostatic discharge and corona discharge
- Dielectric_breakdown --> redirects to Electrical breakdown
- Glow discharge --> redirects to Electric glow discharge
- Thanks for those links!
- Atlant 14:38, 2 August 2005 (UTC)
- Very good links with equations and theory: Excerpts from Dielectric Phenomena in High Voltage Engineering, F.W. Peek, McGraw-Hill, 1929 - Omegatron 17:44, August 2, 2005 (UTC)
Sparks and arcs
Peek says: "By spark-over is generally meant the disruption of a gaseous dielectric from one conductor to another conductor. Strictly speaking it is the name applied to the initial discharge and not the arc that follows." - 
Gas Discharge Tube
Gas Tubes are ceramic arresters utilizing a spark gap, but often called a spark gap. Why?
- Its a spark gap with ioinsed gas surrounding the elctrodes to make it fire more predicatably/at a lower voltage. The ceramic is just the casing.--Light current 17:14, 23 June 2006 (UTC)
New moving image
THe new image is really great. But is it possible to make it a bit bigger so we can really see whats happening>--Light current 17:50, 23 June 2006 (UTC)
Whoops- looks like a copyvio!--Light current 17:53, 23 June 2006 (UTC)
Any light emission hazards with Jacob's Ladder?
In welding we have always been told not to look at the arc at the point of contact because it is producing a broad spectrum of wavelengths, including damaging UV radiation, which can permanently damage the retina.
Does this same safety rule apply to the arc produced by the Jacob's ladder? Is it unsafe to view the arcing for long periods of time?
(I am already aware of the ionization hazards which produce oxygen and nitrogen ions that reform into reactive compounds.)
Low current (typically 10's or 100's of milliamperes) Jacob's Ladders do not generate appreciable amounts of UV light. However, higher current atmospheric pressure arcs (which generate plasma that's a bright blue-white color) can be a problem. Bert (talk) 05:07, 6 July 2008 (UTC)
I hoped to find here the circuit symbol for a spark gap. Is there a standard one?
Length of HV arc
It says here that arcs are 30kv/cm yet many sources say 10kv/cm
Initial spark breakdown of air at sea level is about 30 kv/cm. However, once you've formed an arc by either breaking down the air or by briefly touching the electrodes together, the voltage across the burning arc is considerably less than this. For example, a welding arc may only have 30-40 volts across it. A high current, high voltage arc (such as a power line fault) may have a potential of 1,000 - 2,000 volts/meter.
I've just been doing some experiments with my Neon sign transformer (15kv, 30mA) and the arcs form at the 1.2-1.5cm range, drawing out to 4-5cm
Given the historical devices mentioned is it fair to dismiss inclusion of UJTs as "unusual"? Agree UJTs are today, but so to are the historical devices here. "special apps" suggest inclusion of unusual devices. Could verification of production figures be of any use in settling this? 18.104.22.168 (talk) 03:38, 23 December 2012 (UTC)
- Device type numbers and power ratings would be interesting. The only unijunctions I've ever used have been small-signal types. Andy Dingley (talk) 10:25, 23 December 2012 (UTC)
- I searched for UJT's being used as protection devices before I removed the content and did not find any references. In the 60s and 70s, UJTs were used to trigger SCRs, so they may have been used in combination for crowbar protection, but the primary protection would be supplied by the SCR and not a bare UJT. Glrx (talk) 22:23, 27 December 2012 (UTC)
Break up article?
Suggest since this article covers a wide variety of devices and applications that it be summarized with links to new wiki pages for important applications, e.g. TSG (Power-switching devices).D A Patriarche (talk) 11:48, 7 February 2014 (UTC)