The conductor size determines:

The size of the conductor is directly related to the amount of electrical current it can safely carry. This is pivotal because each conductor has an ampacity rating, which indicates the maximum current it can handle without overheating. If a conductor is too small for the amount of current flowing through it, it can lead to excessive heat buildup, potentially resulting in insulation failure, fire hazards, or other dangerous conditions.

Understanding this ensures that electrical systems are designed with safety and efficiency in mind, preventing overloading and ensuring reliable performance. The size does not influence the total voltage of the electrical system, the type of insulation required, or the length of the circuit run directly; while these factors are crucial in electrical installation, they are not determined by conductor size.