Question T0A03
From subelement T0 - T0A
In the United States, what circuit does black wire insulation indicate in a three-wire 120 V cable?
Why is this correct?
Black wire insulation indicates the 'hot' conductor in US three-wire 120V cables. The hot wire carries live voltage from the source to the load. The standard US color code is: black = hot, white = neutral, green = equipment ground. This standardization is crucial for safety—electricians and equipment installers rely on these colors to identify which wire carries dangerous voltage and must be switched or fused.
Memory tip
Remember the safety sequence: Black = danger (hot), White = return path (neutral), Green = safety (ground). This color pattern is consistent across all standard US electrical installations, making it a reliable identifier when working with any AC-powered amateur radio equipment.
Learn more
Understanding wire color codes becomes critical when installing amateur radio station equipment that requires proper grounding and safety interlocks. Part 97 emphasizes station safety practices, and proper identification of hot conductors is essential when connecting transceivers, amplifiers, and other equipment to AC power. Always verify wire colors match expected voltage measurements—a multimeter reading should confirm black wires carry 120V relative to neutral or ground in properly wired circuits.
Think about it
Why do you think amateur radio operators need to be especially careful about identifying hot conductors when setting up equipment that may require both low-voltage DC and high-voltage AC connections?