CONVERSION FROM ONE SYSTEM OF UNITS TO ANOTHER This section is organized to be consistent with the discussion of physical quantities and equations of physics. The definition of the six fundamental units of physical quantities is presented for the MKS system of units. The definition of some derived units is then presented in the MKS system. The definitions in other systems of units follow the MKS definitions. This is followed by a table of conversion factors between the MKS system and other systems of units. The MKS system based on the meter, kilogram second was augmented to allow force and energy from electrical quantities to be measured in one rationalized system of units. The system was proposed by Giorgi in 1904. It was adopted by the IEC in 1935 to take effect on January 1, 1940. The electrical to mechanical conversion was chosen to be based on the permeability of free space to be -7L 4Pi x 10 henry per meter. DEFINITION OF FUNDAMENTAL UNITS Meter, fundamental unit of length, defined as the distance between two oL specified lines on a specific bar of platinum-iridium at 0 C at standard atmospheric pressure supported at two neutral points 0.285 meter from the center of the bar. The bar is kept at the International Bureau of Weights and Measures near Paris France. Centimeter, cgs unit of length, defined as 1/100 meter. Feet, English unit of length, defined as 0.3048 meter in U.S. Inch, English unit of length, defined as 0.00254 meter in U.S. -10L Angstrom, unit of length, defined as 10 meter. Kilogram, fundamental unit of mass, defined as the mass of a specific cylinder of platinum - iridium kept at the International Bureau of Weights and Measures. Gram, cgs unit of mass, defined as 1/1000 kilogram. Pound, English unit of mass, the avoirdupois pound is defined to be 0.4535924277 kilogram in the U.S. The apothecary or troy pound is 5760/7000 of the avoirdupois pound. Second, fundamental unit of time, defined as one 86,400th part of a mean solar day. Presently measured by an atomic clock based on the rate of nuclear decay. Coulomb, fundamental unit of charge, defined as the charge required to obtain one newton of force between two such charges at a distance of one meter. Candle, fundamental unit of luminous intensity, defined as the source intensity of 1/60 centimeter square opening of the standard light source of a glowing cavity with temperature equal to that of solidifying platinum. A point source of one candle radiates one lumen per steradian. Degrees kelvin, fundamental unit of temperature, defined as zero where the molecular activity of gases cease. The scale is based on zero degrees centigrade (Celsius) for the freezing point of water and 100 degrees centigrade at the boiling point of water. Zero degrees centigrade is 273.16 degrees kelvin. Radians, fundamental unit of angle, defined as the angle formed by a length of circular arc being equal to the radius creating the arc. DEFINITION OF DERIVED UNITS Newton, unit of force, defined as the force required to accelerate a mass of 1 kilogram at 1 meter per second per second when acting continuously. Dyne, cgs unit of force, defined as the force required to accelerate a mass -5L of 1 gram at at 1 centimeter per second per second. One dyne is 10 newton. Poundal, English unit of force, defined as the force required to accelerate a mass of 1 pound at 1 foot per second per second. One poundal is -10L 7.23300 10 newton. A poundal based on earth's gravitation is 32.174 pounds avoirdupois. Joule, unit of energy, defined as work done by 1 newton acting through a distance of one meter. Erg, cgs unit of energy, defined as work done by 1 dyne acting through a -7L distance of one centimeter. One erg is 10 joule. Kilogram calorie, large calorie, unit of energy, is the heat required to raise the temperature of 1 kilogram of water from 1 degree centigrade at a stated temperature. i.e. Kg Cal(22 C). The mean kilogram calorie is defined as 1/100 of the heat required to raise the temperature of 1 kilogram of water o oL from 0 C to 100 C. The small calorie is the gram calorie equal to 1/1000 of a large calorie. One mean kilogram calorie is 0.000238889 joule . British thermal unit, B.t.u , unit of energy, the heat required to raise the temperature of 1 pound of water 1 degree Fahrenheit at a stated oL temperature. i.e. B.t.u.(39 F). The mean British thermal unit is defined as 1/180 of the heat required to raise the temperature of 1 pound of water from o oL 32 F to 212 F. One mean B.t.u. is 0.00009480 joule. Mole, kilogram molecule, is the number of kilograms of a substance that corresponds to its molecular weight divided by 1000. In the cgs system of units a mole, gram molecule, is the number of grams of a substance that corresponds to its molecular weight. The mass of a single molecule in kilograms is the kilogram molecule divided by Avogadro's number. For atoms the molecular weight is the atomic weight. Steradian, sr, is the ratio of the area of the intercepted surface of a sphere to the radius of the sphere squared. 4Pi steradians means the total area of the sphere is intercepted. Watt, unit of power, defined as work done at a constant rate of one joule per second. Horsepower ( mechanical ), English unit of power, defined as work done at a rate of 550 foot-pounds per second. One mechanical horsepower is 745.705 watt. Horsepower ( electrical ), English unit of power, by definition exactly 760 watt. Ampere, unit of electric current, defined as the current that will flow through a circuit with a resistance of one ohm when one volt is applied. The international standard is defined as the current which will deposit silver at a rate of 0.00111800 gram per second. One international ampere is about 0.999835 absolute ampere. International electrical units are based on physical standards whose specifications are slightly in error. Instruments made after January 1, 1948 are calibrated in absolute units. Notes: The singular form of units is used with the exception of foot and feet. Proper names appearing in units and constants are not capitalized. References: Conversion Factors and Tables by Zimmerman and Lavine Electric and Magnetic Fields by Stephen Attwood Elements of Physics by Shortley and Williams