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# From where do we get Volt unit? why 1 volt not 1 s/e =1.4 v?

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#### Hishamsaleh

##### Full Member level 1
I was wondering why do we use Amper, volt, farad, etc... units???? what is the thing or the experiment that let us know that this quantity of capacitance (for example) is 1 unit of farad!!!! i think it must be like meter unit.. it's the wave length of something that gives light with this length as i remember!! that's ok... but how about farad? Amper? volt? from where do we know it?

i'll be thanks if you have information about it....

also where can we find 1 ohm in nature??? what is our reference??? is it like bar???

Do you mean "Why SI, MKSA or other system?"

Here is a link for unit's systems history and MKSA choice.
Pro and con for MKSA, MKSA vs Gauss........

Maybe somebody (or something !) will translate it for you !

Regards

hundred years ago

All of this goes back for at lest a hundred or two years. There were several unit systems used by different science and technology areas. There were many conferences starting near 1900 on making a universal set of units. These discussions also included wheterr 2 pi should be in E&M equations or not by changing the definition of physical constants. Finally around 1960 or so the SI unit system was universally adopted even thoug the electric and magnetic units were not compatible.

No need to translate the french version. There is an english version available as well at this link: **broken link removed**

ok that's gr8... thanks a lot...

sorry if i wasn't clear enough... but what I mean is:

(for example)
what is Pi?
to answer w must know that Pi=22/7... so what's 22/7? from where did we get this number? ok... pi tends to the ratio between (outer length of a cyrcle) / (diameter of this cyrcle)... so, for each 7 units of diameter lengh we know that the outer length of this cyrcle must be 22 unit...

hope you get my point!

my question is:
from where did we get:
1-Volt
2-ohm
3-Amper
and what ever you know of other units...