RE: New Inductance Formula

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

Original poster: "David Thomson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <dave-at-volantis-dot-org>

Hi Shaun,

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

You are correct that I missed the pi.  But the actual expanded formula is:

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

And this formula, while it gives the correct units, is 356% greater than
Wheeler's when:

R = .61m
l = .305m
N = 411.5

Dave