Rationalized system of units

This is the Hagen-Poiseuille law for laminar flow in tubes. Its conversion to a form applicable to experimental measurements will be given later. For the present we note that the quantities R, aP and I can all be obtained by direct measurement and Eqn 4-8 therefore can be used in the absolute experimental method for the determination of the viscosity of a liquid in any physically rational system of units. When the... 

SI units Syst me International d Unit s the international system of units now recommended for all scientific purposes. A coherent and rationalized system of units derived from the m.k.s. units, SI units have now replaced c.g.s. units and Imperial units. The system has seven base units and two dimensionless (formerly called supplementary) units (see Appendix), all other units being derived from these nine units. There are 18 derived units with special names. Each unit has an agreed symbol (a capital letter or an initial capital letter if it is named after a scientist, otherwise the symbol consists of one or two lower-case letters). Decimal multiples of the units are indicated by a set of prefixes whenever possible a prefix representing 10 raised to a power that is a multiple of three should be used. 

The system of units employed almost exclusively in the field of magnetism is the electromagnetic cgs system. The reason is that most experimental results in the literature arc expressed in terms of the quantities y or y. If a rationalized system of units would be chosen by defining B = H + Af, the experimental results would have to be multiplied by 4 n. Consequently, the units commonly employed and also used in this volume are. in case of y, 10 emu g (observe emu/g = cg.s/g=cmVg) and, in case of y, 10 emu/molc (ob.serve emu/mole= cgs molc = cm /molc). Similarly, the units for a and cr are usually taken as 10" Gauss-emu/g and 10" Gauss emu mole, respectively. 

SI units (Systeme International d Unites) The internationally adopted system of units used for scientific purposes. It has seven base units and two dimensionless units, formerly called supplementary units. Derived units are formed by multiplication and/or division of base units. Standard prefixes are used for multiples and submultiples of SI units. The SI system is a coherent rationalized system of units. 

SI (Systeme International) The International System of units a collection of definitions of units and symbols and their deployment. It is an extension and rational ization of the metric system. See also Appendix IB. side chain A hydrocarbon substituent on a hydrocarbon chain. 

In 1960, the eleventh General Conference on Weights and Measures recommended the International System of Units (Systeme International d Unites), abbreviated as SI units, for use in science SI units are essentially the rationalized mks system of units. Relations between SI units and Gaussian units are given in Table A.4 of the Appendix. Table A.5 allows one to convert equations from SI to Gaussian units. 

Given two popular systems of units, SI (= Systeme International, or rationalized MKSC, or Giorgi, or MKSA) and the older cgs (centimeter-gram-second) system, we give first two fundamental equations, Coulomb s law of 1785 and Ampere s64 law of 1826, in both systems. 

Table G Definitions of the Electric Field E, the (Di)electric Polarization P, the Electric Displacement D, the Magnetic Field H, the Magnetization M, the Magnetic induction or flux density B, statement of the Maxwell equations, and of the Lorentz Force Equation in Various Systems of Units rat. = rationalized (no 477-), unrat. = the explicit factor 477- is used in the definition of dielectric polarization and magnetization c = speed of light) (using SI values for e, me, h, c) [J.D. Jackson, Classical Electrodynamics, 3rd edition, Wiley, New York, 1999.]. For Hartree atomic u nits of mag netism, two conventions exist (1) the "Gauss" or wave convention, which requires that E and H have the same magnitude for electromagnetic waves in vacuo (2) the Lorentz convention, which derives the magnetic field from the Lorentz force equation the ratio between these two sets of units is the Sommerfeld fine-structure constant a = 1/137.0359895...

The basic electrostatic units (esu), however, are the unrationalized cgs units. Hence, to convert from unrationalized cgs units to the rationalized mks system of units, start with the relationship... 

All macroscopic aspects of the statics and dynamics of electromagnetic field in the presence of material media are described by Maxwell s equations. The differential form of these axioms in the International System of Units (SI) or rationalized MKS system (Cohen and Giacomo, 1987 Lide, 1991) is given in... 

It is recognized at this time that the English Engineering System of units cannot be completely replaced by the International System (SI). Transition from the English system of units to SI will proceed at a rational pace to accommodate the needs of the profession, industry, and the public. The transition period will be long and complex, and duality of units probably will... 

Heaviside-Lorentz units A system of units for electric and magnetic quantities based upon c.g.s. electrostatic and electromagnetic units. They are the rationalized forms of Gaussian units and, like the latter, are widely used in particle physics and relativity in preference to the S1 units now employed for general purposes in physics. They are named after Oliver Heaviside (1850-1925) and Hendrik Lorentz (1853-1928). 

Sutro, A. (1868). The mineral resources of the United States and the importance and necessity of inaugurating a rational system of mining with special reference to the Comstock Lode and the Sutro Tunnel in Nevada. Murphy Baltimore, http //www. sfmuseum.org/sutro/bio.html P... 

A physical unit system is implicitly defined by the choice of three underlying base units, which suffice to determine dimensionally consistent units for other measurable physical quantities. (Why three such base units are required is as yet an unanswered physical question.) Although the choice of units may superficially appear arbitrary, it was recognized by Gibbs (in his first scientific communication)1 that one can rationally address the question of the conditions which it is most necessary for these units to fulfil for the convenience both of men of science and of the multitude. ... 

According to the modern convention, measurable quantities are expressed in SI (System Internationale) units and replace the centimetre-gram-second (cgs) system. In this system, the unit of length is a metre (m, the unit of mass is kilogram (kg) and the unit of time is second (s). All the other units are derived from these fundamental units. The unit of thermal energy, calorie, is replaced by joule (1 J = 107 erg) to rationalize the definition of thermal energy. Thus, Planck s constant... 

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