Re: Tesla Coil Blunders

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-uswest-dot-net>" <m.j.watts-at-massey.ac.nz>

On 29 Mar 01, at 17:57, Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
> <Parpp807-at-aol-dot-com>
> 
> John, Matt,
> 
> The DC resistance of my bipolar coil is 
> 250 Ohms. The resistance mesaured by the B-K bridge at 1 kc is 270
> Ohms. What resistance is this? If it's not X sub L at 1 kc, how can I
> calculate it?
> 
> Happy day,
> Ralph Zekelman

Hi Ralph,
           Making an accurate prediction of what value ESR will take 
in a resonator prior to winding it depends on a lot of things, not 
least an *accurate and correct model* of the resonator together with 
its resonant frequency and a host of environmental factors. If one 
views the coil as lumped using the "traditional" values for 
inductance and Cself (Wheeler and Medhurst), then it is derivable 
simply by knowing those two values and measuring Q as accurately as 
you can:

ESR = SQRT(L/C)/Q 

Otherwise you can use ESR = Xl/Q

Note that there is a frequency dependence implicit in both those 
equations.

Regards,
malcolm