Douglas Krantz - Technical Writer - Describing How It Works
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What is a Short Circuit?

A short circuit may look like a little spark, but it can lead to danger later.
What you see is a spark and the circuit breaker blows. But there is danger of later fires if hidden problems aren't fixed.


By Douglas Krantz

A short circuit is usually thought of as a spark that almost instantly trips a circuit breaker in the fuse panel of the home. A short circuit does more than that, though. A short circuit is an electrical path that allows the electricity to run wild.

The reason the electricity runs wild is that normally a light bulb, a refrigerator, a furnace, or other load on the electricity holds down the electrical flow through the wires, like having a small hole at the end of a water pipe. The small hole only lets a little water out at a time.

When there's a short circuit, however, the electricity doesn't go through the light bulb, the refrigerator, or furnace. Instead the electricity is taking a shortened path through part of the device, or maybe the short is in the cord or wiring and the electricity doesn't even get to the appliance.

Unlike that small hole at the end of the pipe, the electricity flashes around the device like water gushing out the end of broken pipe.

Sometimes a spark can be seen, sometimes there's just a smell of burnt material, and sometimes nothing is seen or smelled, the circuit breaker is just blown.

Problems with a Short Circuit

Other things happen, though, when there's a short circuit. Engineers have carefully designed electrical circuits and appliances so the electricity will flow in the wires and in the appliances, and will not flow where it can cause injury or fire. A short circuit is an untended electrical path going around the safety features that were designed for the electricity.

No one can predict were the flood of electricity is going to flow when it travels around the intended circuit. Hopefully a person isn't in the way, and hopefully the wires don't heat up causing a fire with the gush of electricity flowing through them.

But beyond that, often there's some charring of some of the connections and materials around the short circuit. After the short circuit is stopped, these complications may still be there. Sometime later, when just a normal amount of electricity is used by an appliance or other electrical device, the charred connections or material could become problematic. Any charring or weakened connection needs to be fixed or it can cause a fire months to years later.

Almost Instantly is not Instantly

Remember the word "almost" that was used when describing how fast the circuit breaker trips when there's a short? Well, this is electricity. During that "almost" time, lots of electricity flowed, and during that "almost" time a lot of damage can occur.

When there's a short, make sure that the cause of the short circuit is fixed, and also make sure to inspect the whole electrical circuit for hidden damage.
Based on his electronics training, and his understanding of Life Safety, Douglas Krantz has compiled his knowledge of Conventional Fire Alarm Systems into the book Make It Work - Conventional Fire Alarms. The book covers the basics of the Conventional Fire Alarm System, and shows how Life Safety and internal supervision affects the fire alarm system.

Douglas Krantz -- Fire Alarm Engineering Technician, Electronic Designer, Electronic Technician, Writer

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