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Increasing gauge numbers give decreasing wire diameters, which is similar to many other non- Metric gauging systems. This seemingly-counterintuitive numbering is derived from the fact that the gauge number is related to the number of Drawing Operations that must be used to produce a given gauge of wire; very fine wire (for example, 30 gauge) requires far more passes through the Drawing Dies than does 0 gauge wire. Note that for gauges 5 through about 14, the wire gauge is effectively the number of bare solid wires that, when placed side by side, span 1 inch. That is, 8 gauge is about 1/8" in diameter. In the same fashion, AWG is also commonly used to specify Body Piercing jewelry sizes. FORMULAS By definition, No. 36 AWG is 0.005 inches diameter, and No. 0000 is 0.46 inches diameter. The diameter increases by 0.46/0.005 = 92 times, evenly divided into 39 sizes. Therefore, the diameter of a No. ''n'' AWG wire is : and its cross-section area is : For an ''m''/0 AWG wire, use ''n'' = −(''m''−1) in the above formulas. The ratio between successive sizes is the 39th root of 92, or approximately 1.122932. The sixth power of this ratio is nearly 2.0, which means for an increase in 6 gauge numbers, the wire diameter is changed by a ratio of two (No. 10 is about one-half the diameter of No. 4 AWG). An increase of three gauge numbers doubles the area of a wire. An increase of 10 gauge numbers, for example from No. 10 to 1/0, multiplies the area and weight by approximately 10 and reduces the resistance by approximately 10. TABLE OF AWGS AND APPROXIMATE CORRESPONDING SIZES The table below shows various data including both the resistance of the various wire gauges and the allowable current ( Ampacity ) based on plastic insulation. The diameter information in the table applies to ''solid'' wires. Stranded Wire s are calculated by calculating the equivalent Cross-section al copper Area . The table below assumes DC or frequencies equal to or less than 60 Hz operation of the wires and does not take Skin Effect into account. The "Approximate stranded metric equivalents" column lists commonly available cables in the format "number of strands / diameter of individual strand (mm)" which is the common nomenclature describing cable construction within an overall cross-sectional area. Where a common cable is midway between two AWG sizes, it is listed and being > one AWG and < another AWG. Cables sold in Europe are normally labeled according to the combined cross section of all strands in mm&2, which can be compared directly with the ''Area'' column. In the North American electrical industry, conductors larger than 4/0 AWG are generally identified by the area in thousands of circular mils (kcmil), where 1 kcmil = 0.5067 mm&2. A ''circular mil'' is the area of a wire one Mil in diameter. One million circular mils is the area of a rod with 1000 mil = 1 in diameter. An older abbreviation for one thousand circular mils is ''mcm''. The term 'mil' is capable of being misinterpreted because the term 'mil' is used sometimes as a colloquial term for millimetre, millilitre etc. Outside North America, wire sizes for electrical purposes are usually given as the cross sectional area in square millimetres. International Standard manufacturing sizes for conductors in electrical cables are defined in IEC 60228 . |
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