# Re: K Quiz

```Subject:  c
Date:   Fri, 23 May 1997 19:52:01 +0000
From:   "John H. Couture" <couturejh-at-worldnet.att-dot-net>
To:   Tesla List <tesla-at-pupman-dot-com>

At 04:16 PM 5/21/97 +0000, you wrote:
>Subject:   Re: K Quiz
>  Date:    Wed, 21 May 1997 07:58:08 -0400 (EDT)
>  From:    tesla-at-america-dot-com (Bob Schumann)
>    To:    Tesla List <tesla-at-pupman-dot-com>
>
>
>>Subject:  K Quiz
>>  Date:   Tue, 20 May 1997 14:14:03 -0400 (EDT)
>>  From:   msr7-at-po.cwru.edu (Mark S. Rzeszotarski, Ph.D.)
>>    To:   tesla-at-pupman-dot-com
>>
>>
>>Hello coilers,
>>        Here is a little food for thought.
>>     "K" is the term applied to the degree of magnetic coupling between

-----------------------------------------    Big Snip

>>Regards,
>>Mark S. Rzeszotarski, Ph.D.
>>
------------------------------------------------------------

>I do not have enough data to make a determination
>to fill in missing K values. Though you have
>stated M for the first setup, it is missing for
>all the others. I can not solve for K without
>the known value of the variable M. When using
>different value coils, the measurements for
>fields aiding and fields bucking will change
>for each substitution therefore changing the
>value of M, a critical value needed in the
>determination of K. You said assume the primary
>and secondary coils aligned on a flat plane.
>If there is a way to calculate M from this
>geometry, I am not aware of it. IMO as soon as
>you change out 1 coil for another, the field
>interaction changes and M must be re-calculated
>prior to solving the coefficient of coupling.
>
>I've got my flame-proof suit on so have at it! Heheh
>
>Bob Schumann
>
>tesla-at-america-dot-com
>http://www.america-dot-com/~tesla
>
-----------------------------------------------------

Bob -

You are correct. There is not enough data to solve the K Quiz because
there are two unknowns. However, there actually is a way to solve this
problem if you have the following information.

In Terman's Radio Engineering Handbook there is a complicated equation
for
finding the mutual inductance of coils configured like a Tesla coil.
This
book is out of print but you do not need to know the equation. All you
need
to know is that in the equation the mutual inductance (Lm) varies
directly
as the secondary coil turns. For example the Lm for the 288 turn coil is

Lm = (288/888)(375.2) = 121.7 uh

I will leave the rest of the problem up to you.

John Couture

```