----- Original Message ----- From: "James R. Frysinger" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]> Cc: "U.S. Metric Association" <[EMAIL PROTECTED]> Sent: Saturday, 2002-07-13 22:52 Subject: Re: [USMA:21030] Re: Fwd: Energy unit TWH
> 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. Jim, I'm not saying the watt-hour is not a unit of energy, of course it is. I'm saying the watt-hour is not an SI unit of energy, only the joule is. Sorry if I didn't make it clear. John > > 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
