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Re: a variable frequency resistor
both inductors and capacitors store energy - 1/2Cv2 in a capacitor. but the
impedance, which is what you call resistance if it is frequency dependent,
has the characteristics I stated. you can determine this for yourself by
looking at the equations for current through each, if you like - remember,
E=IR, so if you can calculate E and I, you have an R. My old pickett slide
rule has a whole bunch of scales for calculating impedance as a function of
frequency for RLC circuits. But you can do it on paper, just use kirkov's
law.
----- Original Message -----
From: Tesla List <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Saturday, May 08, 1999 1:10 PM
Subject: Re: a variable frequency resistor
> Original Poster: Jim Monte <JDM95003-at-UCONNVM.UCONN.EDU>
>
>
> >Date: Fri, 07 May 1999 11:29:56 -0600
> >To: tesla-at-pupman-dot-com
> >Subject: a frequency-variable resistor Re: request for braid data
> > (was Another grounding question)
> >
> >Original Poster: "Bill Noble" <william_b_noble-at-email.msn-dot-com>
> >
> >aaah, wouldn't a frequency variable resistor be an inductor? (if you
wanted
> >more ohms with increasing freq) Or perhaps a capacitor??? (for the
opposite
> >effect)
> <snip>
>
> Not really. Both inductors and capacitors only store energy and give
> it back later. The "give it back later" can be a problem since it may
> result in something just about as bad as what you were trying to
> filter out. Terry has a nice oscillogram on his web site somewhere
> that shows this happening in a neon transformer filter. Resistors
> will dissipate energy as heat, and consequently it cannot come back
> again to haunt you. So resistors are a bit more fail-safe if you are
> not sure exactly what you will be getting for an input. Of course you
> pay for this in terms of greater losses.
>
> Jim Monte
>
>
>