kilopascal wrote:
>
> 2002-07-13
>
> The terawatt-hour is not an SI unit. There is only one SI energy unit, the
> joule. The terawatt-hour is a combination of an SI unit, the watt and the
> non-SI time unit, the hour.
>
> The watt-hour is a unit accepted with limited use along with SI, but it in
> itself is not SI.
....
John,
I have to disagree with you here. The joule is a specially named derived
unit provided for energy. But other derived units, without special
names, can be and are used to express quantities of energy, such as the
newton meter, the watt second, the pascal cubic meter, and so on.
Marvelously, due to the coherence of the system, the numerical factor
that relates each item in that short list above to the joule is "1".
Since the hour is accepted for use with the SI, the watt hour can be
used to represent quantities of energy, but since the hour is not a
coherent unit within the SI, the conversion factor is
1 W.h = 3.6 kJ
with the period on the line in W.h representing the raised dot for
multiplication.
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
