# Re: Tom Heiber <theiber-at-lonet.ca>

```Subject:  Re:   Tom Heiber <theiber-at-lonet.ca>
Date:   Fri, 30 May 1997 16:33:59 -0400
From:   Tom Heiber <theiber-at-lonet.ca>
Organization:  Power Surge
To:   Tesla List <tesla-at-pupman-dot-com>
References:
1

Tesla List wrote:
>
>     From:  Tom Heiber <theiber-at-lonet.ca>
> > Organization: Power Surge
> >          To:  tesla-at-pupman-dot-com
> >
> >
> > This is an equation I got from Bert Pool's file.
> >
> >
> > =======================================================================
> >     EQUATION 10: CAPACITANCE OF A TOROID
> >                                                     ___________________
> >                                                    /    2
> >          C =(1+ (0.2781 - d2/d1)) x  2.8  x      /  2 pi  (d1-d2)(d2/2)
> >                                                /   -------------------
> >                                             \/      4 pi
> >
> >
> >      C = capacitance in picofarads (+- 5% )
> >     d1 = outside diameter of toroid in inches
> >     d2 = diameter of cross section (cord) of toroid in inches
> >
> >     Equation courtesy of Bert Pool
> >
> > =======================================================================
> >
> >
> > CAN ANYONE help me solve for D1 as in D1=........
> > I have been trying to do this without any results (I suck at math)
>
> Turns out to be a bit of a horror.
>     Firstly, the original can be considerably simplified (assuming
> the form above is correct):
>
>    C = ( 0.695 - 2.5(d2/d1) ) x SQRT( d2(d1-d2) )
>
> As far as I've got with attempting to extract d1 (hopefully no
> errors):
>
> (C^2)/d2 = 0.476d1 - 3.9d2 + 3.425(d2^2) + (d2^2)/d1 - (d2^3)/(d1^2)
>
>     I have reservations about all this anyway because it doesn't
> factor in the proximity of the toroid to the resonator.
>
> FWIW,
> Malcolm

Thanx. I'll check it with other results. (I got 4 diffrent resluts). But
thanx for trying even if it's not right :)

Tom Heiber

```