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a fuse being tested with a multimeter

Fuses

Originally contributed by Jeff Butler • last updated 1/7/2021

Did you know that Thomas Edison patented the fuse in 1890 when he invented his electric distribution system? Nowadays, there are so many different kinds, it’s hard to choose a fuse without knowing the basics first.

Definition

In general, fuses are sacrificial electrical safety devices that are designed to stop the flow of electricity if there is a problem. Fuses are commonly found in automobiles, home electronics and appliances, and in older home fuse boxes. Fuses can come in a variety of shapes, sizes, and capacities, depending on their application. Fuses are similar to circuit breakers because they both stop electricity when there is a problem. However, unlike circuit breakers that can be reset, fuses are designed for single use and must be replaced.

How To Tell If A Fuse Is Blown

Fuses are commonly used as electrical safety features in automobiles and many modern home appliances and electronic devices. And sometimes, they need to be replaced. There are a couple of ways you can tell if a fuse is blown:

  • In many cases, you’ll be able to see a visible gap in the wire or a dark metallic smear inside the fuse if it is blown. If you see either, you’ll probably need to replace the fuse.
  • If you are unsure if a fuse is blown, you can test it by using a multimeter. By measuring for continuity, you can determine whether or not the circuit is complete or open.
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