A solenoid is a long, coiled, metal wire through which an electric current is run, resulting in the generation of a magnetic field. Solenoids are often incorporated into more complicated devices which take advantage of this phenomenon, and many of these are simply called solenoids, but are, more accurately, specific types of solenoid device, such as a solenoid switch or solenoid valve. Certain types of components, or solenoid parts, are common to many of these devices.
Any device that is called a solenoid must contain, at the minimum, certain solenoid parts, primarily some type of coiled wire, which can accept an electric current. This is the basis for all such devices, and without one, it cannot properly be called a solenoid, although some devices with equivalent operations or purposes are sometimes called solenoids. Sometimes, the coil is wrapped around a core of metal, usually iron. The device must also have connectors for electric current, both positive and negative, and an insulated housing for the coil as well as mounting hardware to install the solenoid in its proper location.
The most common type of solenoid device is a solenoid switch. It operates by converting the magnetic field generated by the solenoid coil into mechanical action. A piece of metal, often a simple rod that is affected by magnetic fields, moves when the solenoid is energized and closes an electric circuit, activating some other function or operation. Some devices of this type may perform other simple mechanical functions. This type of solenoid, and others that work in the same way, are called electromechanical solenoids.
Another type of solenoid switch is called the solenoid valve. The metal rod, which can be called by a number of names, including slug, armature, rod, and bar, is attached to a valve. When the solenoid is activated or deactivated, it opens or closes the valve.
Rotary solenoids are designed to use the magnetic field generated by a solenoid to create rotary motion. This type of solenoid uses a metal disk instead of a bar as the armature, and usually has ball bearings. An iron core in the solenoid coil itself is almost always present in this type of solenoid. Some types of solenoid may have armatures with gears or other complex shapes to produce a certain type of mechanical activity when energized.
Other solenoid parts are more related to the functions enabled by the solenoid, rather than the structure of the solenoid itself. Solenoid parts, by this classification, can include any number of mechanical or electric components such as contacts for electric circuits, pneumatic valves, switches, and hydraulic controls. Some solenoids may be connected to electronic controllers, capacitors, circuit boards or other electronic components.