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The temperature of the wires can be high enough to cause a fire. If their insulation melts, arcing may occur. Arcing can cause a fire in the area where the overload exists, even inside a wall.

In order to prevent too much current in a circuit, a circuit breaker or fuse is placed in the circuit. If there is too much current in the cir- cuit, the breaker “trips” and opens like a switch. If an overloaded circuit is equipped with a fuse, an internal part of the fuse melts, opening the circuit. Both breakers and fuses do the same thing: open the circuit to shut off the electrical current.

If the breakers or fuses are too big for the wires they are supposed to protect, an overload in the circuit will not be detected and the cur- rent will not be shut off. Overloading leads to overheating of circuit components (including wires) and may cause a fire. You need to recognize that a circuit with improper overcurrent protection devices—or one with no overcurrent protection devices at all— is a hazard.

Overcurrent protection devices are built into the wiring of some electric motors, tools, and electronic devices. For example, if a tool draws too much current or if it overheats, the current will be shut off from within the device itself. Damaged tools can overheat and cause a fire. You need to recognize that a damaged tool is a hazard.

Damaged equipment can overheat and cause a fire.

Wet conditions hazards

Working in wet conditions is hazardous because you may become an easy path for electrical current. If you touch a live wire or other electrical component—and you are standing in even a small puddle of water—you will receive a shock. Damaged insulation, equipment,

Section 5

circuit breaker—an overcurrent protection device that automatically shuts off the current in a circuit if an overload occurs

trip—the automatic opening (turning off) of a circuit by a GFCI or circuit breaker

fuse—an overcurrent protection device that has an internal part that melts and shuts off the current in a circuit if there is an overload

Circuit breakers and fuses that are too big for the circuit are dangerous (e.g., using a 30 amp fuse in a 20 amp circuit).

Circuits without circuit breakers or fuses are dangerous.

Damaged power tools can cause overloads.

Wet conditions are dangerous.

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