[TCML] Cold Sparks and Hot Sparks

[Jeff Behary <electrotherapy@xxxxxxxxxxx>]

Hey All,
 
Last night I was preparing the place for some guests, and I decided to take some pictures of two simple things with Tesla Coils.  I think they are interesting though, because they show two extremes of Tesla Coil discharges - one a cold, crackling spark and one a hot fiery one.
If you watch the videos, please turn on your speakers to maximum volume - the sound (at least on my computer) at this level is close to what the real thing sounds like.  The cold sparks are unusually loud, and hot sparks are unusually quiet.  Tesla mentioned in the lectures that one sounded like gun shot, and the other the hissing of a low frequency arc.  I think he was right!  In the hot spark, it was taken from a bipolar 9" Pancake arrangement powered by a MOT, .05 mfd oil-filled cap, and 4 series 1/2" tungsten spark gap.  The cold spark photos were taken with the recently made Kinraide Coil repro, .096 mfd, single 1/4" tungsten spark gap, and around 2kV also for the tank xfmr. 
The hot spark photos had two steel dischargers, around .080" in diameter.  They actually flare up in little arcs once in a while and started to melt at the tips...both poles were active.  The cold spark photos were between two spheres, 6" sparks.  One was simply an aluminum pipe that touched the primary coil, the other was the active terminal from the coil.  The hot sparks required about 1200 watts, and the discharge could be drawn to around 8" maximum, but the flare ups ceased at over a 2" distance.  The cold sparks were about 150 watts of power.
To take either spark to a metal rod held in your hand a bit unpleasant.  The hot coil makes your whole hand and half of your arm heat up (diathermy), the cold spark causes occasional muscle contractions, some really unpleasant.  
Pictures:
http://www.electrotherapymuseum.com/2008/BipolarFire/Fire.htm
 
Movies:
http://www.electrotherapymuseum.com/2008/BipolarFire/TBKCrackle.wmv
 
http://www.electrotherapymuseum.com/2008/BipolarFire/Fire.wmv
 
Jeff Behary
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