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Re: Secondary Inductance



Tesla List wrote:
> 
> Original Poster: "Steve Young" <youngs-at-konnections-dot-com>
> 
> Hi list,
> 
> I would like to know if the inductance of a secondary space wound to a
> given length with a given number of turns has about the same inductance as
> if close wound with larger wire but the same number of turns?
> 
> For example, suppose I close-wind an 8 inch diameter coil with a winding
> length of 30 inches with 1000 turns of #21 wire.  If I space wind another
> coil with 1000 turns of # 23 to the same 30 inch length, is the inductance
> approximately the same as the close-wound coil?
> 
> If someone has a Wheeler-like equation which has an additional parameter
> representing  spacing of the winding of a TC secondary, I would appreciate
> you posting it on the list.
> 
> Thanks,
> 
> Steve Young

The inductance won't vary by much.. The inductance is mostly a function
of the linking of flux between turns. Same number of turns in the same
volume, etc. is going to have about the same amount of flux linkage,
etc.  

In general the inductance of a wire gets lower as the diameter gets
bigger. However, the bigger wire now can "intercept" more lines of flux,
so the tradeoff might be a wash.

I note that the old NBS circular C74, which is quite complete in
general, doesn't really address wire diameter with respect to the
inductance of a single layer solenoid. However, there is a discussion of
various wire shapes, etc. in the section on toroids. I haven't gone
through it in detail, but that might be a place to look.  Also, if you
have a copy of Terman around, he probably addresses it.