fuse, electric,safety device used to protect an electric circuitelectric circuit,
unbroken path along which an electric current exists or is intended or able to flow. A simple circuit might consist of an electric cell (the power source), two conducting wires (one end of each being attached to each terminal of the cell), and a small lamp (the
..... Click the link for more information. against an excessive current. A fuse consists essentially of a strip of low-melting alloy enclosed in a suitable housing. It is connected in series with the circuit it is to protect. Because of its electrical resistanceresistance,
property of an electric conductor by which it opposes a flow of electricity and dissipates electrical energy away from the circuit, usually as heat. Optimum resistance is provided by a conductor that is long, small in cross section, and of a material that conducts
..... Click the link for more information. , the alloy strip in the fuse is heated by an electric current; if the current exceeds the safe value for which the fuse was designed, the strip melts, opening the circuit and stopping the current. The fuse housing is designed to resist the pressure generated if the overcurrent vaporizes the alloy strip, provided the voltage across the fuse does not exceed its rating. Some fuses, called slow-blow fuses, are designed to carry a small overload for a short time without opening the circuit, while others are designed to open very rapidly if the rated current is exceeded. The choice of one type or the other depends on the ruggedness of the equipment to be protected and whether large pulses of current often occur in the circuit; a slow-blow fuse is usually used to protect motors, and a fast-blow fuse to protect electronic equipment. A circuit can also be protected by a circuit breakercircuit breaker,
electric device that, like a fuse, interrupts an electric current in a circuit when the current becomes too high. The advantage of a circuit breaker is that it can be reset after it has been tripped; a fuse must be replaced after it has been used once.
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