Basic Electrical Question 1

[barmyarmy]

Hi
Excuse this question, I am an mechanical engineer, I was asked the following question by my son who is revising for his GCSE's and like a good dad said I would find out. I asked my electrical colleagues and they dont know the answer.
His question to me was "in Ohmls law, why is current represented by the letter I, when Volts are V and Resistance is R?"
Sorry if this is a little off topic but it certainly brought out some wild guesses amongst my colleauges.


Thanks
Rich

 

[rovineye]

I= German word for intensity. Voltage is also represented as E, E = EMF = electro motive force.

 

[electricpete]

Interesting trivia question. I never even wondered about that... just has always been I.

Google led me to:

http://wiki.answers.com/Q/Why_Ohm_chose_symbol_I_for_current

Apparently it came from the french word but the Germans were involved.

Also you can't call both current and capacitance C or you'd have some confusion.

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[jraef]

There is a slight problem with the original question as well, because the basic premis is mixing electrical math formula symbolism with SI unit symbolism.

When a math formula uses "I" for current, to be consistent one would need to use "E" for voltage, not "V". "V" is the SI symbol for voltage, so consistency would dictate that you would use "A" for amperage in that context. Only the "R" for resistance remains the same for both electrical math formulae and SI units.

But when expressing a math formula for working with electricity, you use the standard math symbols, not the SI unit symbols.

http://www.sengpielaudio.com/calculator-formulasymbol.htm

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[IRstuff]

An amusing, but slightly misleading missive. See:

http://www.mb.fh-nuernberg.de/bib/textarchiv/Ohm.Die_galvanische_Kette.pdf

for the original work by Ohm, wherein, and as described in:

http://www.answers.com/topic/georg-ohm,

Ohm's work does not actually use our notation for I = V/R, instead, he used S = A/L.

TTFN

FAQ731-376

 

[benta]

Being from continental Europe, I've never used V as symbol for voltage, but U. E would be electric field strength.
It seems the use of V for voltage is an English/American tradition, or?

Benta.

 

[jraef]

I wonder if Russians use "W" for "Woltage" then?

[apologies to Walter Koenig, a.k.a. 'Chehov' in Star Trek]