Technician exam question T0A08
Subelement T0, SAFETY· Group T0A
Where should a fuse or circuit breaker be installed in a 120V AC power circuit?
- A.In series with the hot conductor only (correct answer)
- B.In series with the hot and neutral conductors
- C.In parallel with the hot conductor only
- D.In parallel with the hot and neutral conductors
WhyA fuse or circuit breaker should be installed in series with the hot conductor only in a 120V AC power circuit. A fuse or circuit breaker belongs in series with the hot conductor only, so that a fault trips it and disconnects the energized side of the circuit, answer A. Placing one in the neutral as well (B) leaves the hot conductor still live even after the neutral trips, a genuine hazard, and wiring a protective device in parallel with a conductor (C, D) wouldn't interrupt current flow at all, that's not how a fuse or breaker functions.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2026-2030 NCVEC Element 2 pool (public domain); the explanation above is original writing, see our methodology.
Related questions
- T0A01Which of the following is a safety hazard of a 12-volt storage battery that lacks internal protection circuitry?
- T0A02What health hazard is posed by electrical current flowing through the body?
- T0A03In the United States, what circuit does black wire insulation indicate in a three-wire 120 V AC cable?
- T0A04What is the purpose of a fuse in an electrical circuit?
- T0A05Why should a 5-ampere fuse never be replaced with a 20-ampere fuse?