Re: for Inductance Calculation

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

Original poster: "Jim Lux by way of Terry Fritz <twftesla-at-uswest-dot-net>" <jimlux-at-earthlink-dot-net>

>     The formula L=Nr*2/9r+10h........for a single layer air coil.
>
> Matt, the 9 and 10 in the denominator equation, are those a constant of
> some sort??? and of what sort???

That's the Wheeler formula, and is an approximation for single layer coils
that accounts for things like end effects, etc.

>
> This is the formula I have;  L=N(squared) x permeability x A / l
>
> L is inductance in henries
>
> N is # of turns
>
> Permeability is a constant of 1  (for air cores)
>
> A = area of core
>
> l = length of coil
>

That's the formula for an idealized solenoid, ignoring end effects and
"inter turn" interactions.