Re: Theoretical understanding

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

Original poster: Ed Phillips <evp-at-pacbell-dot-net> 

Tesla list wrote:
 >
 > Original poster: Harvey Norris <harvich-at-yahoo-dot-com>
 >
 > --- Tesla list <tesla-at-pupman-dot-com> wrote:
 >  > Original poster: "Godfrey Loudner" <ggreen-at-gwtc-dot-net>
 >  >
 >  >
 >  > Hello Ralph
 >  >
 >  > You can find the stuff in "Introduction to
 >  > Theoretical Mechanics, Robert
 >  > Becker, McGraw-Hill, 1954". Always go the old
 >  > classics in matters of
 >  > classical physics. The new books are nice, but they
 >  > don't treat classical
 >  > topics in great depth and are not comprehensive.
 >  > They are like the soup
 >  > before the main meal, but the main meal is never
 >  > served.
 >  >
 >  > Godfrey Loudner
 > In the booklet by George Trinkaus caled "Radio Tesla"
 > he states the equation for a coils inductance as the
 > familiar L= (N*A)^2/[9A+10B]; but then he notes that A
 > is the length of the winding, and B is the diameter,
 > both in inches.
 >
 > This bugged me because it didnt sound right, and I
 > distinctly remebered using that equation where B
 > instead was the height parameter. So I started going
 > through all my physics and related books to find the
 > correct answer.  Would you beleive none of these books
 > had that elementary definition? I ended up finally
 > finding it in the trusty Pocket Ref Manual by Thomas
 > Glover, which has already come in handy for a myriad
 > of other uses, such as finding winds/per inch for wire
 > gauges ect... I never thought at the time to look
 > under the Pupman main page, which obviously would also
 > have had the definition. But we'd be surprised how the
 > larger texts often omit what some consider to be
 > essential building information.
 >
 > Sincerely HDN

	Correction:  A is the RADIUS of the coil, not its diameter.  That's
Wheeler's simplest approximation, which is good to about 1% for all
values of 2a/l less than three.  That is plenty "good enough for
government work", but there are plenty of more accurate formulae for
those who want to indulge in the extra arithmetic.

Ed