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Why must a 5-amp fuse not be replaced with a 20-amp fuse?

The larger fuse could allow enough current to cause a fire.

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  1. Excessive current could cause a fire ✔
  2. The larger fuse would blow sooner
  3. Power-supply ripple would increase

Why: A 20-amp fuse permits far more current before opening. Wiring designed for 5 amps could overheat before that larger fuse reacts.

Huh, didn't know that: Fuse ratings protect the circuit's wiring and components, not just the fuse itself.

The dad joke
The five-amp fuse said, Please respect my limits.
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References

Answer: Excessive current could cause a fire. A 20-amp fuse permits far more current before opening. Wiring designed for 5 amps could overheat before that larger fuse reacts.

  1. NCVEC 2026-2030 Technician Question Pool www.ncvec.org/downloads/2026-2030%20Technician%20Pool%20and%20Syllabus%20Public%20Release%20Feb%2019%202026.pdf
    C. Excessive current could cause a fire
    Checked 2026-10-09.

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