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Short circuit
Beginner
Low-resistance path causing huge current.
A near-zero resistance path causes a huge current I = ε/r, heating wires and perhaps starting fires. Fuses and breakers disconnect it.
12 V battery with r = 0.01 Ω gives 1200 A.
A short is a low resistance, not a broken circuit.
In more detail
A short circuit occurs when current bypasses the normal load through a path of very low resistance. The current can become very large, causing heating, fire or damage.
Real-world uses
- Fuses and circuit breakers are designed to interrupt short circuits.
- Electricians test wiring for shorts before energising.
- A short circuit, such as a wire touching both terminals of a battery, can overheat and damage the battery very quickly.
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Frequently asked questions
Why is a short dangerous?
The current is limited only by the source, so wires can overheat quickly.
What should I do if a fuse blows?
Find and fix the fault before replacing the fuse with the correct rating.
Why is a short circuit dangerous?
The resistance is almost zero, so the current becomes very large, which generates heat and can start fires.
Related topics in Current Electricity & Circuits
Batteries · Charging and discharging batteries · Electric circuits symbols · Series vs parallel in homes · Drude model · Hall effect