fuse

A fuse is a protective device used in electrical circuits to interrupt current if it exceeds a safe level. It consists of a fusible element, typically a metal wire or alloy, enclosed in glass, ceramic, or polymer housing with end terminals. When the current surpasses the fuse’s rating or a fault causes excessive heating, the element melts or vaporizes, breaking the circuit and isolating the protected equipment.

Fuses vary by construction and response characteristics. Common forms include cartridge fuses (glass or ceramic tubes with end caps) suitable for general electrical use; blade fuses used in automotive and some consumer electronics; and resettable fuses, such as polymer PPTC devices, which increase resistance instead of opening the circuit and can be reused after cooling. Fuses are categorized by response time: fast-acting and time-delay (slow-blow) types. They also differ in current rating, voltage rating, and breaking capacity.

Operation and selection: a fuse is chosen by current rating, voltage, ambient temperature, and the expected fault duration. The fuse should carry normal operating current and blow quickly under fault conditions; otherwise nuisance blows may occur. When a fuse opens, it cannot be reused unless it is a resettable type.

Applications: electrical power supplies, consumer electronics, automotive systems, and industrial equipment rely on fuses to limit damage from short circuits and overloads. Standards and safety: fuses are manufactured to international standards and require appropriate holders and clear labeling.

History: fuses were developed in the late 19th century, evolving from simple wire links to standardized cartridge and blade designs, improving protection, reliability, and replaceability.