Ohm was the FIRST STANDARIZED ELECTROMAGNETIC UNIT. AMPERE WAS THE
SECOND ONE.
To the imbecile Jan:
https://ethw.org/System_of_Measurement_Units#Evolution_of_Electromagnetic_System_of_Units***************************************************************
Evolution of Electromagnetic System of Units
In 1861 a committee of the British Association for the Advancement of
Science (B.A.) was appointed to consider standards of electrical
resistance. The committee decided to adopt a series of electrical units
in the C.G.S. absolute system. The unit of resistance in the C.G.S.
magnetic system was so small (one-billionth of an ohm) that it was
considered unfit for practical use and a unit 109 times greater than the
C.G.S. unit was selected as of convenient magnitude. This decimally
derived unit was called the ohm after the German scientist Dr. Ohm.
Similarly, the C.G.S. magnetic unit of electromotive force was regarded
as unfit for recommendation, and a unit 108 times greater than the
C.G.S. unit was selected, and called the volt, after the Italian
electrician Volta. The ohm having been selected as a unit, standard
resistance coils had to be produced and adjusted-a work of great labor.
In 1864 and 1865, certain standards of resistance or B.A. ohms were
produced and put into service. In 1872, Mr. Latimer Clark produced the
well-known zinc-mercury standard cell which bears his name.
B.A. ohm too small. In 1878, it was realized that the B.A. ohm was too
small by over 1 per cent. That is, the B.A. ohm is now taken to be
0.9866 of the existing international ohm.
In 1881 an international electrical congress at Paris recommended that
the standard ohm should be represented as the resistance of a uniform
column of mercury, 1 sq. mm. in cross-section, at 0 deg. cent., the
length of such a column for the B.A. ohm being approximately 104.9 cm.
The Paris congress of 1881 also adopted the ampere, coulomb. and farad,
as the practical units of• current, quantity and capacity. The practical
system based on the ohm and volt thus became virtually the Q.E.S.
(quadrant-eleventhgram-second) system, in place of the C.G.S. system;
i.e., as though 10^9 cm. were substituted for 1cm as the unit length,
and 10^-11 g. instead of 1 g. as the unit mass.
In 1882, an international commission met at Paris and adopted a length
of 106 cm. as the length of the mercury column defining the ohm, as a
closer approximation to the true ohm than the B.A. ohm. This 106-cm. ohm
was called the "legal" ohm, as distinguished from the B.A. ohm. Legal
ohms, volts, etc., have at the present date almost completely
disappeared. They represented an intermediate stage of approximation to
the present international unit values.
In 1889, an international electrical congress at Paris adopted the
joule, the watt, and the quadrant, as the practical units of energy,
power and inductance, respectively.
Edinburgh conference. In 1892, a conference was held in connection with
the B.A. meeting at Edinburgh. It was then decided to adopt 106.3 cm. as
the length of mercury column whose resistance should 'embody’ the ohm.
In 1893, the international electrical congress of Chicago adopted the
106.3-cm. ohm, which was called the international ohm. The other units
of the practical system adjusted in conformity to this value were called
correspondingly the international ampere, volt, coulomb, etc. The name
of the unit of inductance was changed from the quadrant to the Henry, in
honor of the American physicist of that name.
In 1900, an international electrical congress at Paris, after some
debate, adopted the Maxwell as the unit. of magnetic flux and the Gauss
as the unit either of magnetic intensity or of flux-density in the
C.G.S. magnetic system.
In 1908, an international commission at London considered the order of
sequence of resistance, current and voltage standards, which had been
left indefinite at preceding congresses. It was decided that the ohm
should be the first unit, and the ampere the second, as determined by
the rate of electro-deposition of silver under specified conditions.
The volt was to be determined from the ohm and ampere.
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Meanwhile, E=mc^2 was adopted BY WIDESPREAD USE (BEFORE CONSENSUS) since
1926.
The use of ElectronVolt is closely related to this generalized use. 1933
Chadwick's paper on the "discovery" of the neutron was a landmark for
the
generalization of E=m (no c).
In chemistry, it use allowed this science to grow up as a serious
science, based on mathematical frameworks, that never had a chance
before E=mc^2.