the field lines come out of N (north pole) and go into S (south pole).A bar magnet, with several curved lines pointing from the north to south pole It would be difficult to draw the results from the sort of experiment seen in the photograph, so we draw simple magnetic field lines instead. The tiny pieces of iron line up in a magnetic field. The permeability of lead is low and has basically no affect on magnetic fields.Although we cannot see magnetic fields, we can detect them using iron filings. While lead blocks or stops radioactive emissions such as beta particles or gamma rays, it does nothing to block magnetic fields. Thus, a shell of high permeability material built around an area will effectively keep most of the magnetic field lines in the actual shell itself and out of the area inside the shell. The field lines choose the easiest path to travel. While it is not the same phenomenon, this reminds us of the fact that electricity takes the path of least resistance. The high permeability material will "conduct" the magnetic field lines better than its original path. The magnetic lines take that path and stay out of the region you wanted to shield.
By placing a material of high permeability (or at least a permeability higher than the region in question) around the region you wish to shield, you effectively offer the field lines a better path to travel. Magnetic field lines prefer to travel in materials that have certain magnetic properties, namely materials with high permeability. In order to redirect magnetic field lines, you offer them a preferred path. The field lines still must be continuous and eventually close back on themselves. Note that you have not stopped them, just redirected them. Therefore, it is possible to design a region of space relatively void of magnetic field lines because they have been redirected around that region. The field lines can however be redirected. They cannot be stopped and have nowhere to go. Since these field lines must be continuous, they must find a way back to their origin. In the case of a bar magnet, think of field lines exiting from the north pole, radiating through space, and re-entering the bar magnet at the south pole, continuing through the magnet back to the north pole.
The magnetic field lines are closed loops and must be continuous between a north and a south pole. The terminology scientists use is that monopoles (single magnetic poles) do not exist. This is different from electric charges where you can segregate a single positive or a single negative charge. This law basically implies that you cannot separate magnetic poles, that is, you cannot isolate just one pole there must be two magnetic poles, one called north and one south. Now let us investigate this in a bit more detail.Īctually there is a law named Gauss’s law that tells us something about magnetic fields (this law is also one of Maxwell’s equations which explains all electromagnetic phenomena).
You can however redirect the magnetic field lines, which is what some people call magnetic shielding. The short answer is no, there is no shield or substance that will effectively block magnetic fields as such. I have heard lead stops nuclear radiation can you shield or block magnetic fields? February 2004