Re: primary in secondary

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

Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-uswest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
> 
> Original poster: "Kennan C Herrick by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <kcha1-at-juno-dot-com>

> When the primary is larger in diameter than the secondary, causing an
> annular gap to exist between them, would not some of the magnetic "lines"
> pass between the two coils, thus not "cutting" the secondary turns, and
> thus not acting to induce secondary voltage?  I'd think that primary and
> secondary being concentric (of course), of the same nominal diameter, and
> close together would lead to the highest efficiency.  Those more
> experienced correct me if I'm wrong.

The same situation happens if the primary is outside. The annular gap
affects only the coupling coefficient between the coils (and adds some 
insulation). No problem.
The only inconvenience of having the primary inside is that more turns
are necessary for the same inductance that can be obtained with a coil
outside.

Antonio Carlos M. de Queiroz