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[DPRG] Board indication of 120VAC

Subject: [DPRG] Board indication of 120VAC
From: Jeff Sampson jsampson at pobox.com
Date: Wed Jun 1 00:24:31 CDT 2005

Oh, so it is like magic. ;-)

I guess this is the same concept as the ballast transformer on a 
flouresant light. Except it is capacitive reactance instead of an 
inductive reactance.

> Message: 2
> Date: Mon, 30 May 2005 14:17:28 -0500
> From: "Rick Bickle" <rbickle at swbell.net>
> Subject: RE: [DPRG] Board indication of 120VAC
> To: "'Jeff Sampson'" <jsampson at pobox.com>, <dprglist at dprg.org>
> Message-ID: <005a01c5654c$3885f470$6edf6d0a at MERCURY2>
> Content-Type: text/plain;	charset="US-ASCII"
> Jeff,
> No, the capacitor will not dissipate the same power as a resistor.
> In general terms, you can say that the capacitor has reactance Xc given
> by 1/2(pi)FC, and use this to determine the average current flow through
> the circuit branch. Since the capacitor is reactive however, it doesn't
> actually work like a resistor. A capacitor of a given value and
> frequency can only handle a limited current. The current is limited
> because the capacitor's plates can only hold a certain number of
> electrons. This limiting of current does not dissipate power as a
> resistor does. So both resistors and capacitors (and inductors) can
> limit current, but because a capacitor uses a different method, it does
> not dissipate power and generate heat like a resistor.
> That being said, the capacitor will have some internal resistance and
> will dissipate some power. To be more in depth, there is also power
> factor to consider which increases losses too, but for simple circuits
> like this, it's not usually important.
> Rick

Jeff Sampson

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