What does a number following the progression letter in wire coding indicate?

In wire coding, the number that follows the progression letter typically indicates the wire gauge size. This is a critical aspect of electrical wiring because the gauge size directly influences the wire's ability to conduct electricity effectively and safely. Each gauge size corresponds to a specific diameter of the wire, which in turn affects the amount of current it can carry without overheating.

Understanding wire gauge is essential for selecting appropriate wire for various applications, ensuring that the wiring system operates within its safe capacity and adheres to electrical codes. A correctly sized wire helps prevent potential issues such as voltage drop or overheating, which could lead to equipment failure or fire hazards.

The other options refer to important characteristics of wires but do not relate specifically to the numbers following the progression letter in wire coding. The type of insulation refers to the material coating on the wire, the number of circuits pertains more to system design rather than wire identification, and the voltage rating indicates the maximum voltage the wire can handle, but these are not denoted by numbers in the same manner as wire gauge.