Talk:Abampere

Confusion regarding some emu

In the CRC Handbook of Chemistry and Physics (http://www.hbcpnetbase.com/, no open access, unfortunately) the 'emu' is used both as a system of units (like 'SI') and as a unit itself. In the 'Definitions of Scientific Terms' the following definition is given: Emu - The electromagnetic system of units, based upon the cm, g, and s plus the emu of current (sometimes called the abampere). In the section 'Properties of Magnetic Materials" then the formula : $1\,{\text{emu}}\,{\text{cm}}^{-3}=10^{3}\,{\text{A}}\,{\text{m}}^{-1}$ is given on the first page. If 'emu' in this equation stands for the abampere, how is this consistent with 1 emu = 10 Ampere? I'd appreciate if anyone could shed light on this. — Preceding unsigned comment added by 134.94.7.20 (talk) 15:50, 24 January 2012 (UTC)[reply]

The unit of magnetization is emu/cm³, where emu is erg/G, the unit for magnetic moment. 1 emu/cm³ in cgs emu corresponds to 10³ A/m. I should have ignored this very old question, but couldn't resist. Ceinturion (talk) 12:12, 10 June 2019 (UTC)[reply]

Maybe another bit of clarification. When 'emu' is used to denote a unit, it doesn't necessarily denote a unit of current. Rather, it denotes whatever is the appropriate cgs-emu unit for the quantity in question. So when one says e.g. '2.3 emu of electric charge', that should be understood as a shorthand for '2.3 units of electric charge in the cgs-emu system of units'.

For much of their history, most cgs units for electrical and magnetic quantities didn't have special names. One just said e.g. 'the emu (unit) of electrical current' or 'the esu (unit) of magnetic flux density'. You need to know from context what the appropriate units were (say, in terms of the base cgs units). For example, as Ceinturion says, in the expression

1\,{\text{emu}}\,{\text{cm}}^{-3}

, the context shows that 'emu' stands not for 'the emu unit of current', but for 'the emu unit of magnetic moment'. --Reuqr (talk) 18:54, 2 August 2020 (UTC)[reply]

Revisions to article

I have moved from this article to the "Electromagnetism" article text relating to electromagnetic units in general and inserted definitions of only those units (abcoulomb, abhenry, abohm) that relate to the abampere. I suggest that the other articles on these units get the same treatment. I also added to the "abampere" definition. Fbarw 23:21, 17 September 2007 (UTC)[reply]