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Re: MHO to Siemens





On Fri, 28 Feb 1997, W. Barlow Newbolt wrote:

On Fri, 28 Feb 1997, Roger A. Pruitt wrote:

It is customary to use lower case when referring to the unit and upper case
when referring to the person. Upper case is used for abbreviations.

Roger Pruitt

It is not my custom. It may be some other person's custom.

W. Barlow Newbolt

Roger is correct. It the custom of the physics community, and chemistry as
well. It is the custom sanctioned by the recommendations of the
International Commission on Symbols, Units and Nomenclature, whose entire
recommendations may be found in full in any copy of the Handbook of
Chemistry and Physics. There you will find details about the correct form
of abbreviations. (Such as 's' for second, not 'sec'.)

You may also notice that the custom is followed in college textbooks,
and, one hopes, high school texts as well (at least those I've looked at).
It is followed in scientific journals in physics, chemistry and
engineering, and supported by the style manuals of professional societies
which publish these journals. Every physics teacher should have a copy of
the American Institute of Physics Style Manual available, and students
should be encouraged to use it in their written work.

So, it seems to me, that we should be pointing this out to students, and
setting a good example for them by using these customary forms in our own
speaking and writing. It's also a signal that we are aware of the
standards within our profession.

Proper names are capitalized: Hertz, Newton, Joule, Ampere, etc.

Unit names derived from proper names are not capitalized: hertz, newton,
joule, ampere, etc.

Unit abbreviations derived from proper names are capitalized: Hz, N, J, A
etc.

Also,

Symbols for units should not contain a final full stop and should remain
unaltered in the plural, e.g. 7 cm and _not_ 7 cms.

Double prefixes should be avoided when single prefixes are available:
Not kMW, but GW (gigawatt). Not micromicrofarad, but picofarad.

The unit fermi seems an oddball one. Some authorities recommend that its
NAME be just f. As to capitalization, one must ask, are you calling it a
'fermi' derived from Fermi's proper name? If so, you'd abbreviate it 'F'.
But this seems never to be done! If you are calling 10^-15 m a
'femtometer', then of course you abbreviate it 'f', and poor Enrico is
left out in the cold. He joins Mho in that never-never land of lost units.
My latest edition (4th, 1984) of Physics of The Atom By Wehr, Richards and
Adair, speaks of "the _fermi_ _f_ which is 10^-15 meters."

Other standards I often see teachers and textbooks misuse:

Numbers such as '0.876' should _not_ be written '.876'. Retain a zero
before a decimal point.

'Liter' is _not_ an official metric unit. Volumes are expressed in cubic
meters in equations.

*ALL* metric unit names are pronounced with the emphasis on the prefix.
It's KEELO-meter, not kee-LOHM-eter. Don't pay attention to those TV
newscasters who invariably mispronounce it. You know you can't trust them
on such matters when they routinely utter such nonsense as "The car was
traveling at a high _rate of speed_ when it collided with the tree."

A 'ratio' is a quotient of two _like_ things. Density is mass/volume, it
is _not_ the ratio of mass/volume. But specific gravity is a ratio of two
densities.

'Unit' and 'dimension' are not synonyms.

The form 10^-15 and 1xE-15 are acceptable only in e-mail and computer
program listings, not in handwritten or printed work such as lab reports
or published papers. (I see students misusing this frequently, because
they haven't troubled themselves how to learn to use the symbols available
in their word processors.)

Where there are clearly stated standards and conventions in a profession,
it's unprofessional not to learn them and use them. And as teachers, we
need to make students aware of them. We all goof sometimes, and may get
confused in matters such as the fermi, but we ought at least to make a
conscientious effort, and not invent our own standards out of personal
perversity.

A friend who had received his early education in Catholic schools told me
that the religious instruction there was often at variance with official
Catholic church teaching. He said that the Nuns seemed to have their own
version of Catholocism. I sometimes suspect that some high school physics
teachers and textbooks teach their own version of physics, out of synch
with that practiced by professional physicists. Maybe that's because they
don't have much contact with professionals and journals in their
disciplines.

-- Donald

......................................................................
Dr. Donald E. Simanek Office: 717-893-2079
Prof. of Physics Internet: dsimanek@eagle.lhup.edu
Lock Haven University, Lock Haven, PA. 17745 CIS: 73147,2166
Home page: http://www.lhup.edu/~dsimanek FAX: 717-893-2047
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