MindTap AC DC Practice Test

The cross-sectional area of round wire is measured in circular mils.

True False Square mils Square inches

Correct Answer:

True

Explanation:

For round conductors, cross-sectional area is expressed in circular mils. A circular mil is a unit defined so that the area of a circle with a diameter measured in mils equals the diameter squared, giving a direct link between diameter and area without extra factors. Since a mil is one thousandth of an inch, using circular mils lets you read the area from the diameter in mils as simply d^2. This convention is standard in electrical practice because it makes resistance, current capability, and related calculations straightforward. For example, a wire with a 20 mil diameter has an area of 400 circular mils. Using square mils would require multiplying by pi/4 to convert, and square inches are far too large for typical wire sizes. So the statement is true.

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