What tool would you use to determine the size of an unmarked wire?

To determine the size of an unmarked wire, a wire gauge is the most appropriate tool. A wire gauge is specifically designed to measure the diameter of wire and is marked with a series of notches that correspond to standard wire sizes, allowing technicians to quickly identify the gauge of the wire being measured. This is essential in applications where the correct wire size is critical for safety and functionality, such as in electrical systems.

While a multimeter is useful for measuring electrical properties such as voltage, current, and resistance, it does not provide a direct measurement of the physical size of the wire. A caliper could measure the diameter of the wire, but it is not as efficient for this specific purpose as a wire gauge, which is crafted specifically for identifying wire sizes. A voltmeter is used to measure voltage in electrical circuits and is not suitable for determining wire size at all. Thus, the wire gauge is the most accurate and efficient tool to use in this scenario.