The two main types of fuses are those constructed for use with an alternating current and those designed for direct currents. Within each type, there are different styles, several possible construction materials and varying operational functions.
DC current fuses are more prone to arcing because of the continuous power stream, so they are typically larger than fuses for AC circuits. In an AC circuit, the amplitude of the frequency changes from zero to 60 times each second, eliminating the arcing potential and allowing the poles to be closer together and the overall fuse construction smaller.
Many fuses are cartridge style. Cartridge fuses are cylindrical with metal contact points on each end and are typically found in older homes with fuse panels, older vehicles and electrical machinery. Blade-style fuses are used in most newer vehicles and have slim, rectangular bodies with a forked blade that inserts into the contacts. Fuses can be constructed from different materials including, zinc, copper, silver, aluminum and other alloys for internal conducting elements and paper, glass, ceramic and plastic for external packaging.
Fuses are designed to be the weakest link in an electrical circuit. In the presence of an electrical overload, a fuse's job is to disconnect the electrical power and prevent damage to the device it is powering. Most fuses are single-use, which means that once a fuse is tripped, the element is destroyed, and the fuse must be replaced.