Which instrument is proper for determining the diameter of the conductor of electric hookup wire?

The wire gauge is the most appropriate instrument for determining the diameter of conductor wires, such as electric hookup wire. Wire gauges are designed specifically to measure the thickness of electrical wires and are typically calibrated to reflect the American Wire Gauge (AWG) system or similar standards. This system helps standardize the size of electrical conductors, which is crucial for ensuring that the wire can safely handle the required electrical load without overheating or causing other safety hazards.

Using a wire gauge allows a quick and efficient assessment of a wire's diameter, which is essential for selecting wires that fit electrical systems appropriately. A micrometer, while an accurate tool for measuring small dimensions, is not typically used for this specific purpose due to the efficiency and simplicity of wire gauges for electrical applications. An ammeter and a voltmeter are instruments used for measuring current and voltage, respectively, and do not provide information about conductor size.