# Talk:MKS system of units

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## Modern definition

Does the BIPM or any other authority provide a modern definition of the mks system of units? If the mks system of units never had a governing body to rule on a standard definition then the list of mks units might depend on different conventions and different times. For example a "cycle" may or may not have been a unit in the mks system prior to its exclusion from the International System of Units. At least one journal article in a peer-reviewed journal uses the term "cycles/second". See p. 347 of "Magnetic Formulae Expressed in the M. K. S. System of Units" by A. E. Kennelly in Proceedings of the American Philosophical Society v. 76, p. 343 (1936) --John David Wright 20:10, 26 February 2007 (UTC)

If I'm not mistaken (& I wouldn't be too greatly surprised if I were), the SI is an mks system (the metre, kilogram & second are base units in the SI) and thus the BIPM does provide a modern definition. JIMp talk·cont 16:19, 27 August 2009 (UTC)

## mksc units, addition of charge to the MKS system

My old physics book (Sears and Zemansky 1964), after moving beyond Newtonian mechanics into electrostatics, introduces the mksc units [in lower case], cf page 742:

"The mksc unit of mutual inductance is 1 volt/(amp/sec). This is called 1 henry in honor of Joseph Henry".

Where the volt is defined in terms of the "potential energy per unit charge" (cf p 569). When I interrogate wikipedia "mksc" does not come up to physics articles. Anybody out there know what's going on with respect to the addition of "charge" (c) to the mks unit system? Thanks, Bill

## The fourth unit

Giorgi did not specify that the ampere should be the additional unit. He proposed that a fourth unit , an electromagnetic one, be added. He did not suggest that this should be a unit drawn from a field of engineering; please do not be misled by a false friend. The ampere is a unit from the field of electromagnetism; it is not and was not specifically an engineering or technological unit. NebY (talk) 11:42, 8 March 2015 (UTC)

@NebY: ampere is the SI unit of electric current, not only in the field of electromagnetism, read electrotechnology, fields are very various: electricity, electronics, electromagnetism, telegraph, telephone, electric power, etc. The fourth unit after the tree fundamental units is ampere. Trackteur (talk) 11:59, 8 March 2015 (UTC)
Describing the ampere as a unit of electrotechnology is akin to describing the metre as a unit of building construction. The ampere was indeed eventually chosen to provide the fourth unit, but that choice came long after Giorgi's original proposal and was not inherent to it or an inevitable consequence of it. There were other candidates, such as the volt - yes, SI could have been built on an MKSV system instead, still in accordance with Giorgi's proposal.
I should add that the MKS system pre-dated Giorgi and Giovanni Giorgi is misleading in this respect. NebY (talk) 12:42, 8 March 2015 (UTC)
@NebY: Thank you, now with this chronological explanation I realized my mistake. Regards. Trackteur (talk) 13:42, 8 March 2015 (UTC)