In the United States, what circuit does black wire insulation indicate in a three-wire 120 V cable?
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.
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 Application
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.
Key Concepts
Why Other Options 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.
题目解析
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.
考试技巧
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.
记忆口诀
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.
实际应用示例
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.
错误选项分析
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.
知识点
Wire color coding, Electrical wiring, Hot conductor, Electrical safety
Verified Content
Question from official FCC Technician Class question pool. Explanation reviewed by licensed amateur radio operators.