American Wire Gauge Wire Standards
Wire gauge refers to the thickness or diameter of a wire. AWG, which is short for American Wire Gauge, is a standard mainly used in North America. This is important because the gauge of a wire affects its performance, such as its ability to carry a current and voltage. The AWG standard is used for wire made of metals such as copper, gold, and silver.
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History
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AWG is also known as the Brown and Sharpe wire gauge. The company that developed it was JR Brown and Sharpe, which was based in Providence, Rhode Island. One of the partners, Lucien Sharpe, developed and introduced the company's measuring system to the Waterbury Brass Association in 1856. The association and several companies subsequently introduced it to the world over a year later. The Birmingham Wire Gauge was the standard AWG superseded, and it is still used today for iron. There are several other types of wire gauge standards, such as the British Wire Gauge and Music Wire Gauge.
Features
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AWG ranges from 0 to 40. Additional measurements are 00, 000, and 0000. The thicker the wire, the smaller the gauge number, and the higher the wire diameter. A gauge of 40 is the thinnest, and a gauge of 0000 is the widest. The measurements are taken without regard to the presence or thickness of the insulation the wire may have, since insulation does not affect a wire's conductivity.
The units of measurement are in inches or millimeters. The cross sectional area of the wire, which is the square of the diameter, has its own special terminology. It is referred to as a circular mil or mils, where 1 mils = 0.001 inch.
AWG standards apply to wire that is solid or composed of strands.
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Significance
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Wire gauge standards are important because thicker wire is needed for high currents than for small currents. Like water flow in pipes, electrons can move more easily in thick wires than it can in thin ones, because there is less resistance. A low gauge number therefore means better current flow. Circuits wired with the wrong gauges can cause electrical shock or death, equipment damage, and fire.
Current Ratings
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Resistivity is defined as the resistance per unit length. Common units for wires is ohms per meter or ohms per kilometer. The measurements are assumed for a wire at room temperature of 20 degrees Celsius, because temperature also affects resistance. The AWG, material, temperature, and insulation affects how much current a wire can handle. The maximum amount of current a wire can safely conduct is called the ampacity.
Considerations
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The typical gauge number used in household wiring is 12 or 14, because it can handle an ample amount of current. For example, a copper wire with an AWG of 12 has a diameter of 0.08081 inches, which is 6,530 mils. It has a resistivity of 5.2086 ohms per kilometer, and a weight of 19.778 lbs. per 1,000 feet. It can handle up to 25 to 30 amps. Telephone wire normally ranges from 22 to 26 AWG. Hobbyists commonly use 20 or 22 AWG, with 30 AWG for some circuit boards.
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References
- CableOrganizer.com: The Facts on American Wire Gauge
- "Electronic Components: A Complete Reference For Project Builders"; Delton T. Horn; 1992
- "Electronics For Dummies"; Cathleen Shamieh, Gordon McComb, 2009
- "Electrician's Instant Answers"; Gary Tuck, David Tuck; 2003
- "Electronics Portable Handbook"; Stan Gibilsco; 2000
Resources
- Photo Credit spindle of copper wire on white background image by phizics from Fotolia.com
