Re: secondary question

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

Original poster: Bert Hickman <bert.hickman-at-aquila-dot-net> 

Tesla list wrote:

>Original poster: "Steve Zeitler" <zeitler-at-verizon-dot-net>
>I have seen plenty of coils in person and pictures that produce arcs much 
>longer than the length of the secondary coil. What prevents to voltage 
>from the secondary from just arcing down it's own length? Its the shortest 
>path.
>                                                            Steve Z
>
>.
Hi Steve,

In two words: field control.

Long sparks never take the shortest path. Instead, they progress from a 
high voltage terminal in a series of discrete steps, each step being the 
most opportune at that instant. However, once streamers begin, each step 
will inject an increment of electrical charge into the air in front of the 
streamer. This region  of charged air, called a space charge, now alters 
the electrical field seen by the streamer tip. As a result, the the NEXT 
step may head in a different direction depending on the polarity of the HV 
terminal versus the previous step.

By using a toroid, the maximum electrical field can be made to point 
outward and not downward. This results in streamers being "directed" 
outwards so that most of them will continue heading horizontally without 
terminating. If a given streamer happens to randomly begin heading 
downwards, it may form a relatively long looping arc to ground or the 
primary or strike rail. Field control is one of the key reasons that 
toroids are so popular atop Tesla Coils. By stacking a smaller toroid below 
a larger one, even better field control is possible, allowing the coiler to 
virtually prevent primary strikes. A well designed 2-coil system with tight 
field control can achieve spark lengths that are four times the coil 
height. Richard Hull's magnifier achieved a spark length that was over 
eleven times the resonator length.

Best regards,

-- Bert --
--