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From: rwt@dcs.ed.ac.uk (Rainer Thonnes)
Subject: Re: New IEC proposal: 1 kibibyte = 1024 bytes
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Date: Tue, 14 Jan 1997 16:34:39 GMT
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In article <5bg2jh$na7@lyra.csx.cam.ac.uk>, mnb20@cam.ac.uk (Mark Baker) writes:
> 	rwt@dcs.ed.ac.uk (Rainer Thonnes) writes:
> 
> >The thing is that both the siemens and the hertz are completely unnecessary
> >units, being as they are an inverse ohm and an inverse second, respectively.
> >I assume that the fundamental quantity remains resistance, with conductance
> >being a derived quantity, just as time is more fundamental than frequency.
> 
> How is V/I more fundamental than I/V? I'm not sure I could construct a
> good scientific argument for time being more fundamental than frequency,
> though to our brains it is more fundamental.

I didn't really mean "fundamental" in the philosophical sense, but clearly
both time and frequency and resistance and conductance (that's really neat,
using "both" with four items, and nary a serial comma in sight) are pairwise
related in much the same way as are the chicken and the egg.  It is the case,
though, is it not, that only one of each pair is well-defined in certain
terms, and the other is derived from it.  

Going by the name of the old cgs and mks systems, one would have thought
that the second should be the more fundamental, but SI is a bit coy in this
respect.  There the second is listed as an elemental unit, and the frequency
unit is expressed in terms of the second, but nevertheless the definition of
the second is essentially in terms of the frequency of a particular type of
radiation.

A similar oddity exists with respect to electric charge and current.  There
exists a fundamental constant of nature, e, the charge of an electron, and
yet they prefer to give the ampere rather than the coulomb the honour of
being an elemental unit, and define the C as being an As, and to make
matters worse, they've defined the A in terms of the force, of all things.

Anyway, SI defines the ohm as a VA^-1 and the siemens as an ohm^-1, thus
affording the ohm somewhat greater prominence.  Still, we need neither of
them.  Your "ten ohm resistor" has a resistance of 10 newton meters per
square ampere per second, unless you'd rather say that its conductance is
0.1 square ampere seconds per newton-meter.

> >I think the mho must have two plurals, one as you say, the other without
> >the 's'.  The same goes for the ohm.
> 
> I would always say "the resistance is ten ohms" rather than "ohm".

You're probably right, I may be confused by my upbringing.  In German the
plurals of all the units except the second are indistinguishable from the
corresponding singulars.
