Re: Wire length, coil geometry, and velocity factor

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

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 27 Jul 2004, at 13:15, Tesla list wrote:

 > Original poster: "Paul Nicholson" <paul-at-abelian.demon.co.uk>
 >
 > First, some news of more progress...
 >
 > We know from measurements that signals traverse a solenoid winding
 > rather faster than they would do if the wire were straight. Ed
 > Phillips has shown that the apparent speed-up factor relates to the
 > h/d ratio in the manner plotted in
 >
 >   http://www.abelian.demon.co.uk/tmp/ph1.gif
<snip>

 > Ed's tabulated function shows how these two effects compete with
 > each other as h/d varies.  At large h/d, increase of L wins and
 > the velocity is high.  At low h/d, the reduction of C seems to
 > overcome the increase in L and the velocity is low.

This is more-or-less the argument that I've used in the past to
account for the frequency deviation although I didn't think about it
from a velocity point of view. Medhurst's derivation of C vs h/d
ratio is inherently non-linear and has an inflection about h/d = 1 or
so.

Malcolm