Re: Input power vs. Spark length output

I'm not sure how much this has to do with it, but a Tesla coil develops 
and maintains a powerful electromagnetic radiation field and a space 
charge. Generally, the spark discharge is at least initiated at the point 
where the field strength is the highest, and probably follows the field 
lines to some extent.

A longer spark means a larger possible discharge radius, which 
means that a larger total VOLUME of space is being affected, not just 
a longer LENGTH of air.

Steven Roys (sroys-at-radiology.ab.umd.edu)