A passive component
is one that does not have the ability to change its properties like a semiconductor
, but performs a basic electrical function due to its construction and materials. There five types:
- These are energy storage devices. They have layers of insulating material called a dielectric sandwiched between layers of conductor, and electrons build up at the layer junctions.
- These limit current in a circuit, useful for changing voltage. Most are made by mixing graphite powder and clay, with the resistance determined by the clay/carbon ratio. Some are also made by coiling a wire tightly, basically creating a really long path to limit current flow (These were the first type made.)
- These are coils of wire that store energy in the form of a magnetic field. The inductance is directly proportional to the radius of the coil and number of turns.
- These are square or round rings made of stacks of sheet metal that are wrapped in wire, using the magnetic field created to convert voltage. There is a wire for source current and a wire for the output current, with the number of windings on each length of wire determining the voltage conversion.
- These are protection devices that burn out or change their physical characteristics when the current in the line goes above a preset limit. A fuse can have a simple metal strip that melts, or be made from polymeric positive-temperature-coefficient material that changes from conductive to non-conductive when heated by excess current. The latter is referred to as a resettable fuse, as it goes back to a conductive state once it cools down.