Electromagnetic devices are objects powered by electromagnetic fields, producing electricity or magnetized by electricity. They include motors, solenoids, generators, alternators, electromagnets, and electromagnetic coils. Solenoids are used in high-security time locks and electromagnetic bullet devices. Generators produce direct current while alternators produce alternating current. Electromagnetic devices are also used in security alarm sensors.
The term electromagnetic device refers to any object that is powered by electromagnetic fields, produces electricity using magnetic fields, or is magnetized by electricity. Devices powered by electromagnetic fields are classified as electric motors or solenoids. Electric generators and alternators are electromagnetic devices that produce electricity using magnetic fields. Electromagnets and electromagnetic coils make up the third group of electromagnetic devices.
When referring to an electromagnetic device powered by electromagnetic fields, there are two basic branches: the motor and the solenoid. The motor uses electric current to generate magnetic fields within the windings to rotate the motor shaft on its axis. The solenoid only works in two directions of movement. When the solenoid windings are electrically charged, the shaft moves into or out of the coil, depending on the magnetic orientation of the shaft. In some cases, the movement of the shaft may be assisted by a spring.
An interesting example of a solenoid in action is the electromagnetic bullet device. When energized, the coils of this device generate a high magnetic pressure on the magnetized shaft, forcing it out of the coil. The shaft of this electromagnetic device is not constrained and can therefore be ejected from the coil at high speed.
Another application of the solenoid is its use in operating time lock mechanisms for high security areas, such as bank vaults. When these solenoids receive power, the shaft stays in the coils. When the timer cuts power to the coils, a spring pushes the shaft off the coil and into the locked position.
Another group of electromagnetic devices includes those that create electricity from magnetic currents. The simplest form of alternator or generator is actually an electric motor. Instead of using a battery to power the motor, the shaft is turned by hand. The alternator differs from the generator only in its moving parts and electrical power. Alternators produce an alternating current (AC) by moving rotating magnets past the coils. Generators produce direct current (DC) by turning coils of wire rather than magnets.
A third group of devices that bear the name of electromagnetic device includes any object that is magnetized by electricity. Thus the electric motor and generator wire coils can stand alone under the name of an electromagnetic device in their own merit. Other devices that fall into this category are the large electromagnets used in automotive salvage and the electromagnetic coils used in the ignition systems of some automobiles.
In some cases, electromagnetic devices are used as components of security equipment, such as security alarm sensors. In the case of the security alarm sensor, an electromagnetic device is held in close contact with a coil of wire or permanent magnet. When the two elements are kept within range, the circuit remains open and no alarm sounds. When one of the two objects is moved, it generates a change in the electromagnetic field and the circuit closes, triggering the alarm.
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