The toroid nicely protects the top of the secondary/tertiary from breakout by extending the field down and out from the former. You're much more likely to get breakout from the coil top with a sphere (I've tried both).
For a VDG, the sphere provides working room inside for the roller, pickup, etc. and for a given size with have a significantly greater radius of curvature which gives you a higher breakout voltage.
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf Of dave pierson
Sent: 05 December 2013 23:51
To: Tesla Coil Mailing List
Subject: [TCML] Spheres and Torroids
>Hi Fellow HV enthusiasts.
>Why do you use a toroid on top of a Tesla Coil and a sphere on the top
>of a VanDeGraf generator?
Each can be used on eash, sometimes it seems
to be practicality issues. Its easier to
have a roller and combs inside a sphere than
'in' a toroid.
>Being as we are dealing with high voltage, low current applications and
>knowing how these voltages travel on the outside of the conductor,
All voltages (charges....) travel on the outside.
>it would seem likely that the two could be used interchangeably.
And they are, tho some are more commonly used each way.
And perhaps some other comments on the Tesla coil
specifics might be had...
best
dwp
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxx
http://www.pupman.com/mailman/listinfo/tesla