Permanent Magnet And Electromagnet

Permanent magnets are not under external magnetic field, able to keep magnetic objects. Electromagnet with it instead, magnet when carrying a current of magnetic, if the current is cut off, magnetic will disappear. Wire is wound into a coil, it is like a magnet, there are n pole and s pole, it is a simple electromagnet. Solenoid like a permanent magnet has two poles, can attract iron, but is different from permanent magnets, electromagnets and magnetic properties of the magnetic poles can change. 1 ton weight electromagnetic crane used in electromagnets.