Circular mils are the units used to measure the ?

Circular mils are the units used to measure the ?

• A. Length of American conductors
• B. Resistance of wire
• C. Voltage drop of American conductors to and from the load
• D. Cross-sectional area of American conductors

Answer: (D)

Circular mils measure the cross-sectional area of a conductor. A circular mil is the area of a circle with a diameter of 1 mil (0.001 inch). For a wire with diameter d in mils, the cross-sectional area in circular mils is d squared. This unit is used in the American wire sizing system because the area directly affects how much current a conductor can carry and how its resistance behaves: resistance per length is inversely proportional to the cross-sectional area, and voltage drop depends on that resistance and the current. Length, not the cross-sectional area, is measured in inches or feet, and voltage drop relates to resistance and current but isn’t itself a unit of area. So circular mils are used to express the cross-sectional area of American conductors.

Circular mils measure the cross-sectional area of a conductor. A circular mil is the area of a circle with a diameter of 1 mil (0.001 inch). For a wire with diameter d in mils, the cross-sectional area in circular mils is d squared. This unit is used in the American wire sizing system because the area directly affects how much current a conductor can carry and how its resistance behaves: resistance per length is inversely proportional to the cross-sectional area, and voltage drop depends on that resistance and the current. Length, not the cross-sectional area, is measured in inches or feet, and voltage drop relates to resistance and current but isn’t itself a unit of area. So circular mils are used to express the cross-sectional area of American conductors.