The use of generic electric coil with iron core inside, make it like a magnet with a magnetic device called an electromagnet (electromagnet). Usually made of bars or hoofs. The core to use easy magnetization, and easy to disappear or to make soft magnetic properties of silicon steel. Such an electromagnet is magnetic when energized, and then disappears after power is cut off. When the iron core is inserted inside the through solenoid, the iron core is magnetized by a magnetic field of the through solenoid. The iron core after magnetization has also become a magnet, so that the magnetism of the solenoid is greatly enhanced because the two magnetic fields are superposed with each other. In order to make the electromagnet more magnetic, the iron core is usually made into hoofs. Note the winding of the coil on the hoof iron core, on the other hand, clockwise and on the other side against the counter clockwise. If the winding is the same, the magnetization of the two coil to the iron core will cancel each other, so that the core will not show magnetism. In addition, the core of the electromagnet with soft manufacture, and not with the steel making. Otherwise, when the steel is magnetized, it will keep magnetism for a long time, but it can not be demagnetization, then its magnetic strength can not be controlled by the size of current, but the advantages of losing electromagnet should be lost.
The electromagnet has many advantages: there is no magnetic electromagnet with on-off current control; magnetic size can be controlled by the strength of the current or the number of turns of the coil; also can change the resistance control current to control the size of magnetic pole size; it can be made by changing the current direction to control, etc..
Electromagnets are widely used in daily life. Electromagnet is an application of current magnetic effect (electric magnetic field), which is closely related to life, such as electromagnetic relay, electromagnetic crane, magnetic suspension train, etc..
Electromagnets can be divided into two types: direct current electromagnet and AC electromagnet. If the electromagnet is divided according to its use, it can be mainly divided into the following five kinds: (1) traction electromagnet - mainly used to pull the mechanical device and turn on or off all kinds of valves, so as to carry out the automatic control task. (2) - used as a lifting electromagnet lifting device to hoist steel ingot, steel, iron ore and other ferromagnetic materials. (3) brake electromagnet - mainly used for braking the motor to achieve the purpose of accurate parking. (4) automatic electromagnetic system such as electromagnetic relay and contactor electromagnetic system, automatic switch of electromagnetic release and operation electromagnet, etc.. (5) electromagnets for other purposes such as grinders, electromagnetic chucks, and electromagnetic vibrators.