True or False: To calculate circular mils, one should multiply the diameter of wire in thousands of an inch by itself.

The statement is true because circular mils are a unit of measurement used to express the cross-sectional area of a wire. To calculate the area in circular mils, you indeed multiply the diameter of the wire (given in thousandths of an inch) by itself. This calculation is based on the geometric formula for the area of a circle, which is πr². However, since using the diameter directly simplifies the calculation for wire sizing, the formula is adjusted to use diameter instead. Specifically, if you have the diameter in thousandths of an inch, squaring that value provides the area in circular mils, which is a more convenient unit when dealing with electrical wire sizes.

Other choices may imply conditions or variations in calculations that are not necessary for the straightforward computation of circular mils, but the base principle remains consistent regardless of wire type or insulation.