5 December 2012
Copper Wire Sizes (EE)
The diameter of a copper wire is measured by using a system called the American Wire Gauge also known as AWG. This system has predominantly been used in the United States and Canada since 1857. Using this measurement the cross-sectional area of a gauge is able to be found. We then use this area to determine the wires current carrying capacity. The gauge numbers for wire and diameter values work inversely, as when one increases the other decreases. AWG tables are commonly used to portray values for a solid round conductor; however this method can also be used for stranded wires. If you had a wire of each of these types with the same AWG the stranded wires diameter would be larger. The AWG has a 40 different gauge sizes. These sizes begin at 0000 which is the largest in diameter of all the wires with a length of .46 inches. This ranges all the way to size 36 with a length of.005 inches. The following formula solves for the diameter of a number y. D(y)=.005x(92((36-y)/39)). Using the value of the diameter we are then able to find the cross-section area using the following formula. A(y)=(pi/4)xD(y)^2. The resistance of wire also is related inversely to the diameter of said wire. The resistivity for copper varies with temperature. The resistance formula for a copper wire goes as follows: R=TxL/A. In this formula T equals resistivity; L equals length of wire, and A equals cross sectional area. Another major part of copper wires is their current carrying capacity. Not surprisingly the value of amps able to flow through a wire decreases as the diameter of the wire decreases. While charts can give good estimates on these values they are unable to give completely valid answers. This is because when measuring the current carrying capacity you must also consider: voltage drop, insulation temperature limit, thickness, thermal conductivity, and air convection and temperature. The fusing current for a wire...
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