Updated: Dec 9, 2025 | Source: 2022-2026 Question Pool | Topic: T0A
T0A03T0A

In the United States, what circuit does black wire insulation indicate in a three-wire 120 V cable?

Deep Dive: T0A03

The correct answer is B: Hot. In the United States, black wire insulation indicates the hot (live) conductor in a three-wire 120V cable. The standard color coding is: black = hot (ungrounded conductor), white = neutral (grounded conductor), green or bare = equipment ground. For amateur radio operators, understanding wire color coding is essential for safe electrical work. Always follow proper color codes and never assume wire colors - verify with a meter if unsure.

Why Other Answers Are Wrong

Option A (Neutral): Incorrect. White indicates neutral, not black. The neutral is the grounded conductor. Option C (Equipment ground): Incorrect. Green or bare wire indicates equipment ground, not black. Ground is the safety conductor. Option D: Incorrect. Black insulation is used and indicates the hot conductor. It's a standard color in US wiring.

Exam Tip

Black wire = hot conductor. Think 'B'lack = 'B'eware (hot/live). Standard US color coding: Black = hot, White = neutral, Green/bare = ground. Always verify with a meter if unsure.

Memory Aid

Black wire = hot conductor. Think 'B'lack = 'B'eware (hot/live). US standard: Black = hot, White = neutral, Green/bare = ground. Always verify with a meter for safety.

Real-World Example

You're wiring a power outlet. The black wire connects to the brass terminal (hot), the white wire connects to the silver terminal (neutral), and the green wire connects to the green terminal (ground). Following this color code ensures safe, correct wiring. The black wire carries the ungrounded (hot) conductor that can shock you.

Source & Coverage

Question Pool: 2022-2026 Question Pool

Subelement: T0A

Reference: 2022-2026 Question Pool · T0 - Safety

Key Concepts

Wire color coding Electrical wiring Hot conductor Electrical safety

Verified Content

Question from the official FCC Technician Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the T0A topic.