Technician exam question T0A05
Subelement T0, SAFETY· Group T0A
Why should a 5-ampere fuse never be replaced with a 20-ampere fuse?
- A.The larger fuse would be likely to blow because it is rated for higher current
- B.The power supply ripple would greatly increase
- C.Excessive current could cause a fire (correct answer)
- D.Voltage drop in the higher current fuse could result in excessively low voltage to the device
WhyA 5-ampere fuse should never be replaced with a 20-ampere fuse because the excessive current it would allow could cause a fire. A fuse's rating sets the maximum current the circuit's wiring and components are designed to handle safely, so replacing a 5-ampere fuse with a 20-ampere one lets far more current flow before anything interrupts it, which is enough to overheat wiring and start a fire, answer C. The oversized fuse being less likely to blow is exactly the problem, not a reason it's safe (A), and B and D both invent effects, ripple and voltage drop, that a larger fuse rating doesn't actually cause.
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.
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