Which term describes the cross-sectional area concept used with AWG for precise sizing?

• A. Circular mils
• B. Square inches
• C. Millimeters of thickness
• D. Ohms per kilometer

Answer: (A)

The concept being tested is how AWG expresses a conductor’s cross-sectional area. The term used is circular mils. A circular mil is the area of a circle with a diameter of 1 mil (0.001 inch), so the cross-sectional area in circular mils is simply the diameter in mils squared. This makes it easy to relate size to current-carrying capacity: as diameter grows, area grows with the square, which matches how resistance and ampacity scale.

For example, a wire with a diameter of 40 mils has a cross-sectional area of 40^2 = 1600 circular mils. This unit is the standard for AWG sizing because it directly reflects the conductor’s usable cross-sectional area. The other options aren’t used for AWG cross-sectional area: square inches is a different area unit not used in this context, millimeters of thickness is a dimension, and ohms per kilometer describes resistance per length, not area.