MadSci Network: Physics
Query:

Re: Why, when figuring out electric current, is the symbol 'I' used?

Date: Fri Feb 27 16:00:05 1998
Posted By: Ricky J. Sethi, PhD
Area of science: Physics
ID: 887760004.Ph
Message:

Hi Barbie,

This turned out to be a very hard question, indeed! The annals of physics often lead you down dark corridors that, unfortunately, aren't well-documented, and, sometimes, aren't documented at all. I did an extensive search on the Internet, in various physics books, and asked almost everyone even remotely associated with an educational institution (including my 8 year old nephew, who, surprisingly, wasn't very enlightening on this matter and was probably just wondering why Uncle Rick was acting even weirder than usual). All this in vain. In vain, that is, until I gave in to my desperation and posted a message on the sci.physics and the sci.physics.electromagnet newsgroups. Salvation came in the form of one Mark Kinsler who seems to have the best explanation I've come across. So, without further ado, here is Mark's explanation in his own words...


The story I got is that it's French, which often accounts for a lot of
mysteries in this world.  "I" stands for "intensitie" or however it's
spelled--I don't know much French.  I'm afraid that I don't have a
good reference handy.

I probably would have applied "intensity" to voltage, not current, but
at the time all the electrical units were being thrashed out there was
considerable confusion as to what was what.  Also, nobody asked me.

As it stands, voltage became "E," for "electromotive force" in the
English-speaking world and "U," which presumably stands for something
else, everywhere else.  Convention has lately had "E" changing to "V."

But "I" for current seems to be pretty constant all over the world.

My favorite misuse of symbols is becoming standardized in the
electronics newsgroups, I'm sorry to say.  One of the standard
mistakes of beginning electronics students is the use of R as a unit
instead of a symbol.  They'll call a 10,000 ohm resistor a "10,000 R"
resistor, for which they lost credit when they did it in my classes.
But I'm afraid that this usage has become rampant in e-mail, possibly
because there's no handy omega symbol on the computer keyboard.

Mark Kinsler
-- 
.............................................................................
Interpretation and instruction in physical science and technology.
Athens, Ohio, USA.     http://www.frognet.net/~kinsler

Well, I hope that helped. Usually I end my emails with something to the effect that you should feel free to email me if you need something clarified but, in this case, I hope you understand if I defer you to please email Mark! All kidding aside, this was a very interesting question to pursue... and it points out a unique benefit of resources like the Web and the little nooks and crannies (e.g., the Mad Scientist Network :) of this immense, world-wide network. Here was a question that none of the people actively involved in physics (professors, grad students, researchers, etc.) I spoke with knew the answer to. But the world-wide community, the collective mind, so to speak, was able to speak to it. And anything that lets you harness the "collective crania" (to borrow a phrase) of so many people is a powerful resource, indeed!

Just something to consider,

Rick.


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