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 Either electromagnetic or permanent magnet sucker sucker, are inseparable from a "magnetic" words.  In fact, back in the pre-Qin era of our ancestors have accumulated a lot of knowledge in this area, often encountered in the search for iron ore magnetite, that is a magnet (the main ingredient is iron oxide). 

 Is the magnetic material to attract or repel each other as a physical phenomenon. Common magnetic material is iron and magnet, and some steel.  Although generally not a magnetic material, the material in a magnetic field, however, will still be a slight magnetic effect, but in general can be measured with special instruments. 

 Magnetic force is due to motion of electric charges generated by the fundamental forces.  Maxwell's equations describe the sources and behavior of this force law (another reference to Biot - Sand cutting law).  When the charge or charged state of an object in motion will produce magnetic.  Such as "induction" is the moving electrons in the circuit with the phenomenon; and "permanent magnet" is a sub-atomic electron in a fixed spin movement caused by the phenomenon. 

 The intensity of electromagnetic fields occur as distance from the source with the rapid increase and decrease.  Electric field can easily be metal shell, reinforced concrete buildings isolated.  Electrical equipment such as transformers, due to the metal shell, so almost no electric field outside.  It is difficult to isolate the magnetic field, but if the opposite direction, the same size as the current generation of magnetic fields can cancel each other out.  Therefore, the three-phase power transmission over single-phase power line magnetic field generated by power lines will be much smaller.