In fact, everything in the world is magnetic, whether it is the desk stool around us or the composition of material molecular structure atoms, and even large planets have magnetic.  Only some substances are magnetic when they are open to the outside world, and some are not.  When talking about the origin of magnetism, we should start from the origin of matter. It is known that matter is made up of molecular structure atoms, in which there are nuclei and many electronic devices.  Inside the atom, these electrons create magnetic moments and tracks that closely orbit the nucleus.  

When the raw materials of the motor plastic magnetic rotor manufacturer are magnetized, the two plastic magnetic rings suffer from the harm of the external kinetic energy, such as heating and impact. The magnetic distance orientation of the magnetic domains in which will become more and more inconsistent, and the magnetism will weaken or fade. This link is called demagnetization.  There is also a common method: place the reserved magnetic raw material in the communication ac magnetic field, gradually weaken the compressive strength of the communication AC magnetic field until it subsides, and the raw material will be demagnetized.  

Can use strong magnetic permanent magnet material body, the general magnet "magnetic", that is, the general magnet;  Can also be wrapped in a trap on the general magnet, with a large current on the electromagnetic coil charge and discharge of the way, the magnet magnetic (generally with a large power capacitor battery charge several hundred volts, charge and discharge of the electromagnetic coil).  When adding magnetism, pay attention to the direction of the current, so that the magnetic field formed by the electromagnetic coil is consistent with the magnetic field of the magnet.  Basic principle magnet and permanent magnet two difference: the magnetic field of the electromagnet can also be changed, which is determined by the positive and negative of the solenoid and its electromagnetic coil coil orientation.  And permanent magnet field is sure not to change N↔S.  The magnetism of electromagnet can be changed, that is, there is magnetism when plugged in, and there is no magnetism when not plugged in.  And permanent magnet ferromagnetism is its own irrelevant with electricity.