Last modified on 21 June 2009, at 03:03

FHSST Physics/Electricity/Fuses

The Free High School Science Texts: A Textbook for High School Students Studying Physics
Main Page - << Previous Chapter (Electrostatics) - Next Chapter (Magnets and Electromagnetism) >>
Electricity
Flow of Charge - Circuits - Voltage and Current - Resistance - Voltage and Current in a Practical Circuit - How Voltage, Current, and Resistance Relate

- Ohm's Law Analogy - Power in Electric Circuits - Calculating Electric Power - Resistors - Nonlinear Conduction - Circuit Wiring - Polarity of Voltage Drops - Series and Parallel - Simple Series Circuits - Simple Parallel Circuits - Power Calculations - Using Ohm's Law - Conductor Size - Fuses - Important Equations and Quantities

FusesEdit

Normally, the ampacity rating of a conductor is a circuit design limit never to be intentionally exceeded, but there is an application where ampacity exceedence is expected: in the case of fuses.

A fuse is nothing more than a short length of wire designed to melt and separate in the event of excessive current. Fuses are always connected in series with the component(s) to be protected from overcurrent, so that when the fuse blows (opens) it will open the entire circuit and stop current through the component(s). A fuse connected in one branch of a parallel circuit, of course, would not affect current through any of the other branches.

Normally, the thin piece of fuse wire is contained within a safety sheath to minimize hazards of arc blast if the wire burns open with violent force, as can happen in the case of severe overcurrents. In the case of small automotive fuses, the sheath is transparent so that the fusible element can be visually inspected. Residential wiring used to commonly employ screw-in fuses with glass bodies and a thin, narrow metal foil strip in the middle.