Talk:Coulomb

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Does coulomb imply positive or negative charge? Since the ampere per second is conventional current, would it technically be 6.24×10¹⁸ times the charge on a proton? - Omegatron 16:36, May 26, 2004 (UTC)

I think you're probably right. However, I think it probably also makes sense to say "1 coulomb of electrons", knowing that this is the same as -1 coulomb of conventional charge. -- Anon

Er ... I think "does coulomb imply positive or negative charge?" is as meaningful a question as is "does meter imply positive or negative distance?" (or rather, displacement, so that we can actually allow negative values). A unit in itself has no sense of direction, positive or otherwise; it's just a measure of the magnitude.

[edit] no need for a list of binary prefixes. avogadro's number is a common misconception

Discussion moved to Talk:Units of measurement

[edit] Kilogram

<-n00b says : . . . . Kilogram ?!? Please clarify how the kilogram applies.

I don't see how the kilogram note is relevant to this article. Being that it lacks an explanation, it's just an odd little statement.

I see how one can make that statement, but I'm not sure how to fit it into an encyclopedic article, not a physics homework. Anyways, this is how: the definition of ampere states, 1 A is the current such that if 2 parallel wires (at distance 1 m) have 1 A through it, there will be 2e-7 N/m of force on wires. Defining C on its own gives an alternate definition of ampere as 1 C/s, and once ampere is defined that way, we can define newton in terms of ampere, and since newton = m*kg*m/s^2, now we can define kg in terms of newton .... which is defined in terms of ampere and meter, which is defined in terms of coulomb and meter and second.

[edit] note

"The Ampere is in fact a derived unit..." but not according to the Wikipedia entry for Ampere, where it says, "Because it is a base unit, the definition of the ampere is not tied to any other electrical unit."

Given the definition for the Ampere as given in the Ampere entry, I'm inclined to believe that the Ampere is in fact the base unit and the Coulomb is the derived unit, despite the relationship 1 A = 1 C/s.

Correct. The current SI standard defines the ampere as a base unit, for practical reasons. (It is more intuitive to think of the charge on one electron as fundamental unit on which to base the definition of the Coulomb and then base the Ampere upon the Coulomb, but that's not how things are defined in current SI.)

I am suspicious of the article section: "The ampere was historically a derived unit - being defined as 1 coulomb per second. Therefore the coulomb, rather than the ampere was the SI base electrical unit," because what I have read of the history of electrical units did not say that the ampere was figured from coulombs. Here are pages about the history of electrical units:

http://alpha.montclair.edu/~kowalskiL/SI/SI_PAGE.HTML

http://www.sizes.com/units/ampHist.htm