Which characteristic of electrical wire is crucial for determining its current-carrying capacity?

The wire gauge, often expressed in American Wire Gauge (AWG), is crucial for determining the current-carrying capacity of electrical wire because it directly relates to the wire's diameter and, therefore, its resistance. A lower AWG number indicates a thicker wire, which can carry a higher current without overheating. Thicker wires have lower resistance, reducing the heat generated when current flows through them, thus allowing them to carry more current safely.

In addition to the wire gauge, other factors like insulation type, wire length, and environmental conditions can influence current-carrying capacity, but these are secondary to the fundamental role that wire gauge plays in determining how much current a wire can handle. The insulation material does provide certain thermal and electrical characteristics, but it is the gauge that primarily dictates current capacity. Similarly, while wire length does affect voltage drop, it does not change the intrinsic current capacity dictated by the wire's gauge. The color coding of wires is primarily for identification and does not pertain directly to their ability to carry current.