Electrical wire is used to fabricate electrical and electronic circuits. To determine what gauge, or diameter, of wire must be used in a circuit, you must take into account how much electrical current the circuit needs. Using the specifications for a 16 AWG copper wire as an example, you can see how the diameter and length of a wire affect how much electrical current a wire can carry.
Wire diameter is expressed in American Wire Gauge, or AWG. Regardless of the material type, a 16 AWG (or "sixteen-gauge") wire will always be the same diameter - .0508 inches, or 1.29 millimeters.
Current Carrying Capability
A wire's ability to carry electrical current is directly proportional to the wire's diameter. For example, a non-insulated 20 AWG wire -- which has a diameter of .03 inches -- can carry a maximum of 1.5 amperes of electrical current. A 16 AWG wire can carry a maximum of 3.7 amperes of electrical current under the same conditions.
Longer Cables Lose Power
While it is possible to maintain a constant current across the entire length of wire, the voltage at the transmission end of the wire can differ from the voltage at the reception end of the wire. This is because even good electrical conductors present some electrical resistance. Electrical resistance through a 16 AWG copper wire can be calculated by using this formula: (length in feet)x(13.17 Ohms/1000 feet) = Wire resistance in Ohms
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