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 New Online Book! Handbook of Mathematical Functions (AMS55) Conversion & Calculation Home >> Reference Information Handbook of Mathematical Functions With Formulas, Graphs, and Mathematical Tables (AMS55) Purchase the electronic edition of this book in Adobe PDF format! FIRST | PREVIOUS | NEXT | LAST | CONTENTS | PAGE | ABOUT | SMALL | MEDIUM | LARGE Below is the OCR-scanned text from this page: 2. Physical Constants and Conversion Factors The tables in this chapter supply some of the more commonly needed physical constants and conversion factors. * The International System of Units (SI) established in 1960 by the General Conference of Weights and Measures under the Treaty of the Meter is based upon: the meter (m) for length, defined as 1 650 763.73 wave-lengths in vacuum corresponding to the transition *2p,,-5dS of krypton 86; the kilogram (kg) for mass, defined as the mass of the prototype kilogram a t Sevres, France; the second (s) for time, defined as the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of cesium 133; the kelvin (K) for temperature, defined as 1/273.16 of the thermodynamic tem- perature of the triple point of water; the am- pere (A) for electric current, defined as the current which, if flowing in two infinitely long parallel wires in vacuo separated by one meter, would produce a force of 2 /.: lo-; newtons per meter of length between the wires; and the candela (cd) for luminous intensity, defined as the luminous intensity of 1/600 000 square meter of a perfect radiator at the temperature of freezing platinum. All other units of SI are derived from these base units by assigning the value unity t o the proportionality constants in the defining equa- tions (official symbols for other SI units appear in Tables 2.1 and 2.2). Taking 1/100 of the % meter as the unit for length and 1/1000 of the kilogram as the unit for mass gives rise sirni- larly to the cgs system, often used in physics and chemistry. SI, as it is ordinarily used in electromagne- tism, is a rationalized system, i.e., the electro- magnetic units of SI relate to the quantities appearing in the so-called rationalized electro- magnetic equations. Thus, the force per unit length between two current-carrying parallel wires of infinite length separated by unit dis- tance in vacuo is 2f = p0ilil/4~, where- po has the value 4X >( 10-'H/m. The force between two electric charges in vacuo is corresponding- ly given by f = qlq2/4~~or2, €,] having the value l/pclc2, where c is the speed of light in meters per second. (~,,--8.854 x 10-"F/m) Setting pc, equal to unity and deleting 4a from the denominator in the first equation above defines the cgs-emu system. Setting ccB equal to unity and deleting 4~ from the de- nominator in the second equation correspond- ingly defines the cgs-esu system. The cgs-emu and the cgs-esu systems are most frequently used in the unrationalized forms. Table 2.1. Common Units and Conversion Factors, CGS System and SI Factor Quantity Force 1 0 7 - Energy joule (J) Power *See also "Preface to Ninth Printing," page IIIa and page 11. Table 2.2. Names and Conversion Factors for Electric and Magnetic Units ~ Quantity Current Charge Potential Resistance Inductance Capacitance Magnetizing force Magnetomotive force Magnetic flux Magnetic flux density Electric displacement SI name ampere (A) coulomb (C) volt (V) ohm (0) henry (H) farad ( F ) A . m-1 A weber (Wb) tesla (T) .-- ................... - __ emu name abampere abcoulomb abvolt abohm centimeter oersted gilbert maxwell gauss ( G ) esu name statampere statcoulomb statvolt statohm centimeter ______ _____ emu-SI factors lo-' 10-1 108 109 109 10- 9 4rr x 10-3 47r x 10-1 108 104 10-j esu-SI factors -3 x 109 -3 x 109 - (1/3) X 10-2 - (1/9) x 10-11 - (1/9) x 10-11 -9 x 10" -3 x 109 -3/106 - (1/3) x 10-2 - (1/3) x 10-6 -3 x 105 Example: If the value assigned to a current is 100 amperes its value in abamperes is 100 x 10-l = 10. 6 The page scan image above, and the text in the text box above, are contributions of the National Institute of Standards and Technology that are not subject to copyright in the United States.