Indeed.  It looks like Bill's message ended up opening up a Pandora's can of worms 
here...  :-S

Marcus

On Tue, 26 Mar 2002 00:41:15  
 Bruce Hebbard wrote:
>
>On Mon, 25 Mar 2002, Bill Hooper in USMA:19071 wrote:
>
> . . .
>> The watt is also equal to a volt-ampere but that is not it's original
>> definition. The watt is originally defined as a joule per second. Since the
>> volt (V) is a joule per coulomb (J/C) and the coulomb (C) is defined as an
>> ampere-second (A7s), it is easy to show that the volt-ampere equals the
>> watt:
>> 1 V7A = (1 J/C)7(1 A) = (1 J/A7s)7(1 A) = 1 J7s = 1 W
> . . .
>
>That of course being the case, could someone please explain why serious 
>power equipment often uses VA (kVA, MVA, etc.) as distinct from W ?
>
>I recall recently seeing some small computer UPS (or some other
>equipment) that was rated in both VA and W, with *different* numerical
>values given for each.  (Is this an RMS-vs-peak kind of thing?)  This has
>always perplexed me when I see VA used on utility transformers, etc.
>
>Bruce H.
>
>


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