Re: Current Density?

[brian whatcott <inet@INTELLISYS.NET>]

At 23:02 5/1/99 +1000, Brian McInnes wrote:
> ...this t(h)read has strayed a bit from lightning (and that was very
> interesting) but I think your comments about Density are worth
> thinking about.

I advocate that contributors rename a thread's subject line as soon
as they sense a cognitive dissonance between the title and (in my case)
the ensuing divagation.

> That means that the something is any appropriate quantity and the
> space is 3-dimensional or two-dimensional or one-dimensional (or
> n-dimensional, if for example we want to refer to the density of
> states in some kind of phase space).
>
> Now, in physics, if we just say density, the quantity we are probably
> referring to is mass and the space is 3-dimensional, so its a (volume)
> mass density, the ratio of mass to density with SI units kg/m^3.

A descriptive lexicographer easily copes with generalizations of a
term denoting a useful physical ratio, on both the numerator line AND
 the denominator line: he simply accumulates qualified references.

   The prescriptive lexicographer (and there are not many in Science)
looks askance at a usage that comes to mean (as the Queen would say to
Alice) exactly what she means it to mean.


> (By the way, I find the term "per [unit] volume" rather meaningless,
> but that is another story.)

This is an interesting comment that I would be glad to see
developed.   The concept of unit volume in itself is not difficult -
 at least for liquids under gravity: one picks a bottle without leaks
 as a container, and acknowledges that temperature and pressure, maybe
atmospheric humidity are confounding variables.
One thinks of a pyknometer and how this relies on mass measurement:
perhaps that's the cause of Brian's difficulty?
(a certain circularity...)


brian whatcott <inet@intellisys.net>
Altus OK