JAKES LADDER

[HANKMARS]

I have an extra high pressure coil and now have a notion to construct a Jacob's Ladder. At first blush, I had no idea why the active arch would begin to travel upward along the ladder sides, increasing the length of the arc and apparently the resistance thru which the arc must travel. Seems to contradict the "path of least resistance" principle. Further rumination brought about a theory that, as a conductor (metal in this case) increases in temperature its impedance also increases. Therefore, the arc is seeking a path of lesser resistance by way of cooler metal. However, I vaguely recall hearing a theory touting an over abundance of ions is created by the arc and are elevated by the rising heated air produced by the arc and the arc finds that ion track to be a lesser resistance, and follows it. I believe both effects come into play.

 

[bertus]

Hello,

Perhaps this article might interest you:
http://www.electricstuff.co.uk/jacobs.html

Be carefull with those very high voltages.
Safety comes first:
http://www.repairfaq.org/sam/safety.htm

Bertus

 

[HANKMARS]

Electricstuff interesting. repairfaq not so much.

 

[Nanren888]

Hot air?

 

[HANKMARS]

Most likely off track with heated air notion. The arc will produce considerable heat but if free ions (ozone O3 in this case, I would guess) they probably radiate all directions from the arc regardless of convection currents. Not really sure on this.

 

[Sunnysky]

Strong thermal convection forces the flame upwards of >6000’K until extinction voltage is achieved by gap width. Negative resistance of arc is limited by PTC of a tungsten series current limiter so a new arc is less likely to begin from the bottom at the same time as a higher arc. Too small a gap prevents sufficient upward force to move it.

 

[HANKMARS]

Strong thermal convection forces the flame upwards of >6000’K until extinction voltage is achieved by gap width. Negative resistance of arc is limited by PTC of a tungsten series current limiter so a new arc is less likely to begin from the bottom at the same time as a higher arc. Too small a gap prevents sufficient upward force to move it.

RE: Convection currents. Will the arc not travel upwards if unit were in a vacuum?

 

[Nanren888]

Maybe an easier test is to hold it horizontally, or slightly upside down?