Re: New Inductance Formula

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

Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>" <scepp-at-mts-dot-net>

Hello Dave, Antonio, and All

I wanted to know where your correction factor comes from,

>> Add a "correction factor" to the denominator, replacing l by (l+0.9*r):


And Dave, the reason that inductance formula is way off is because it is
missing a "pi", see below:

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, May 03, 2002 6:20 PM
Subject: RE: New Inductance Formula


> Original poster: "David Thomson by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>
>
> Hi Jim,
>
> >>>The inductance of a long solenoid is given, theoretically, by:
> >>> eq1 >L=u0*a*N^2/l H
> >> Where did you find this formula?
>
> >This is sort of the fundamental definition of inductance of a coil...
from
> first principles. You'll find it in any first year physics text.
>
> In the book Physics, by Edward R. McCliment, Univ of Iowa, the formula for
> self inductance is given as:
>
>         4pi * km * R^2 * N^2
> Lself = --------------------
                           l

Should read:

            4 * pi^2 * 10^-7 * R^2 * N^2
Lself = ----------------------------------
                                    l

       which is the expanded version of that physics text inductance formula
for a long selenoid.  I expanded u and area.

--snip--

Shaun Epp