kilopascal wrote:
....
> I'm going to disagree with you for the following reasons:
>
> Will the Authorities on SI ever recognise these other expressions as "energy
> units" or just equivalence's to the joule?
I think that we're not having the same discussion, John. I agree that
the joule is the derived unit provided by the SI to express quantities
of energy. But I disagree with you when you say that the kilowatt hour
is not a unit of energy, except for electrical energy.
Try to understand that, as I teach physics I must convince my students
that the pascal cubic meter is indeed a unit of energy. (Cf: PV=nRT) All
to often, they think that since their answer did not come out in joules
(which they learned first as newton meters), it could not possibly be
so. Of course, "pascal cubic meter" is hardly a very elegant way to
express energy, especially when the specially named derived unit joule
is available. Nonetheless, it is a unit of energy. The distinction
between "is" and "is equivalent to" is too Clintonesque to argue here,
John!
Both the joule and the kilowatt hour are energy units, regardless of
the form of the energy. Energy is energy. But, yes, the joule is solely
SI whereas the kilowatt hour includes the hour, which is merely accepted
for use with the SI (though nowhere does the brochure state any
limitations on that). And, yes, many, many standards (such as the CSA
and SI 10 that Robert quoted) admonish users of the standard that the
authors of those standards do not wish to see the use of kilowatt hours
expand into non-electrical areas.
In otherwords, we're quibbling over wording. I saw nothing in the SI
brochure to support your use of "limited" in your statement, "The
watt-hour is a unit accepted with limited use along with SI." Robert had
to resort to derivative standards to support that point, if you'll
notice, in USMA:21045.
If it makes you feel any better, I also greatly prefer joule to
kilowatt hour and would like very much to see that change made in my
electric bill. My letter to my electrical energy company several years
ago did not change their minds, however.
Jim
--
Metric Methods(SM) "Don't be late to metricate!"
James R. Frysinger, LCAMS http://www.metricmethods.com/
10 Captiva Row e-mail: [EMAIL PROTECTED]
Charleston, SC 29407 phone: 843.225.6789
