Re: A question about LCR circuits

To: tesla-at-poodle.pupman-dot-com
Subject: Re: A question about LCR circuits
From: Tesla List <tesla-at-stic-dot-net>
Date: Sat, 17 May 1997 20:52:53 -0500
Approved: tesla-at-stic-dot-net
Subject:  Re: A question about LCR circuits
  Date:  Sat, 17 May 1997 23:05:38 +0000
  From:  "John H. Couture" <couturejh-at-worldnet.att-dot-net>
    To:  Tesla List <tesla-at-pupman-dot-com>


At 05:26 AM 5/16/97 +0000, you wrote:
>Subject:     Re: A question about LCR circuits
>       Date: Fri, 16 May 1997 07:47:22 +1200
>       From: "Malcolm Watts" <MALCOLM-at-directorate.wnp.ac.nz>
>Organization: Wellington Polytechnic, NZ
>         To:  tesla-at-pupman-dot-com
>

  Malcolm -

  Regarding your reply to my post

----------------------------------------------------

>John, (and anyone interested),
>
>>   You show that   Q = sqrt(L/C)/R   Where did you find this equation? 
>
>I showed the derivation in this very place not two months ago.
>Take Q = wl/R, Q = 1/wLC
>Multiply them to give Q^2 = wl/R x 1/wLC
>do the algebra, then take the square root.
>
>----------------------------------------------
 
 I do not agree that your derivation and your equation Q = 1/wLC  are
correct because an equation for the Q factor must contain a resistance
(R).
The Q equations of which I am aware are -

       Q = wL/R = 1/wCRs = Rp/wL = wCRp  

where Rs = series resistance and Rp = parallel resistance

------------------------------------------------
 
>>   You indicate that the effective resistance (for Tesla coils?) is
>> easily
>> measured. Would you explain this test?
>
>Measure the Q of a coil. The R that pops out of Q= whichever one of 
>the formulae you like to use is the ESR. For high Q air-cored coils it 
>is heavily dependent on the proximity to surroundings.
>
----------------------------------------------------

  Thank you for the method to measure the effective resistance. Note
that at
the design stage for a Tesla coil that both the eff R and the Q factor
are
unknown. This presents a problem for anyone developing a TC computer
program. The JHCTES TC program gets around this problem by using a graph
shown in the TC Notebook. This graph is based on empirical data and
seems to
be working. However, it needs to be verified by other coilers willing
and
capable of doing the work or replacing it with a better method to find
the Q
and R for a classical TC.

 John Couture