# Re: Awg formula, was "New formula for secondary resonant frequency"

```Original poster: "Antonio Carlos M. de Queiroz by way of Terry Fritz <twftesla-at-uswest-dot-net>" <acmq-at-compuland-dot-com.br>

Tesla list wrote:
>
> Original poster: "Ed Phillips by way of Terry Fritz
<twftesla-at-uswest-dot-net>" <evp-at-pacbell-dot-net>

>         Here is a quote from an neat old book of mine which covers the same
> subject:

> No. 0000 is 0.46 inch diameter, and No. 36 is 0.005 inch diameter

This is what I used. 0000 would be n=-3:
Assuming d=10^(a*n+b), and taking decimal logarithms:
log(d)=a*n+b
n=-3 -> d=0.460 inches -> log(0.460)=a*(-3)+b
n=36 -> d=0.005 inches -> log(0.005) =a*36+b
Subtracting: log(0.460)-log(0.005)=-39*a ->
a=-log(92)/39 = -0.05035353
>From the relation for n=36: b=log(0.005)-36*a ->
b=(36*log(0.460)+3*log(0.005))/39 = -0.48830277

>         Let n = number representing the size of wire.
>
>             d = diameter of the wire in inch.
>
>         Then log d = 1.5116973 - 0.0503535 n,                     (187)
>
>          - 0.4883027 - log d
>      n = -------------------                               (188)
>               0.0503535

All the other formulas are just this same formula written in different
ways.

Antonio Carlos M. de Queiroz

```