Which term refers to an area equal to that of a circle with a 0.001 inch diameter?

• A. Conductor
• B. Conductivity
• C. Circular Mil
• D. Capacitor

Answer: (C)

Circular mil is a unit of cross‑sectional area for wires. It’s defined as the area of a circle with a diameter of 0.001 inch. If you take that circle, its radius is 0.0005 inch and its area is π × (0.0005)^2 ≈ 7.85 × 10^-7 square inches. By definition, that area corresponds to one circular mil. In practice, you’ll see wire sizes expressed in circular mils, and the quick relation is (diameter in inches × 1000)^2 equals the area in circular mils. So a wire with a 0.001 inch diameter has 1 circular mil. The other terms refer to different concepts (a conductor is a type of component, conductivity is a material property, capacitor is a component), not this unit of area.