What Does a Wire Capacity Chart Show?


Quick Answer

A wire capacity chart shows the maximum current capacity for a specific wire run. Besides the current-carrying capacity, the chart also shows the wire size, the resistance and the skin effects of an American wire gauge cable.

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Full Answer

The American wire gauge is a standardized norm used to note the diameter of an electrical conducting wire. The chart displays the diameter in inches and millimeters. It also provides a column with the area of the cable or conductor.

The resistance charted in the table is for a specific conductor. Use the resistance for the respective noted current to calculate the voltage drop across the conductor using Ohm’s law that states that the current that passes through the conductor is inversely proportional to the resistance and directly proportional to the potential difference between the two points.

The current ratings displayed in the chart are for power transmission. The rule of 1 ampere per 700 circular mils determines the current rating value. The skin effect listed in the table is that behavior of alternating current that causes it to distribute itself within the cable, in order that the current density near the surface is greater than the density near the core. It affects the effective resistance of the conductor causing it to increase with the frequency of the current.

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