Flat secondary coupling

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

Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Goinbonkers-at-aol-dot-com>

Hi all,   
   In regards to a flat spiral secondary,  I'd like to hear thoughts on the
difference if having the primary coil's OD the same as the secondary,  having
the primary coils 'average' diameter equal to the OD of the secondary, or the
primary coilsID equal to the OD of the secondary. 

    I would seem to me that the first case would have greater capacitive
coupling, but what I really am talking about is the magnetic coupling.   On one
hand the first case might seem to have greater coupling (at a given spacing of
the coils' planes).   On the other hand, in the third case all of the secondary
would be inside the primary's lines of flux. 

    To toss in another notion, what if the primary were wound helically and at
a diameter just a bit larger than the secondary's OD?  If the plane of the
secondary were placed at the midpoint of the helical primary, the voltage
stress  would be lessened(assuming the outside turn of the secondary is
grounded).   
    Ok, last one:  what about a case where the ID of the primary was greater
than the OD of the secondary and one was using a DC power suppy or with one
side grounded.  Then there would be almost no voltage difference between the
outer turn of the secondary and the inside turn of the primary. I think there
would a bit of difference since the secondary would have the opposite polarity
by the end of the first turn, but you could actually connect the primary to the
secondary and ground them together 
   Comments? 
      Mike