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Name: James K.
Status: student
Age: 30s
Location: N/A
Country: N/A
Date: Saturday, April 20, 2002


Question:
Is there a substance that can block magnetic force and act as a shield (such as Nu-Metal or soft iron), but which, unlike these two substances is not affected itself by the magnet. For example, wood is not affected, by a magnet but unfortunately, it is not an effective shield. Is there a substance that can act as a shield but also be unaffected (ie. not attracted to the magnet)?


Replies:
James,

There is not such a material. If you explore the field of magnetism, you will discover something called Ampere's Law. The source of magnetic field is moving electric charges, either through a circuit or around an atom. The only way to shield a magnetic field is to provide electric charges moving in the opposite direction. These two set of moving charges will feel magnetic force between each other.

One example of such a device is coaxial cable: one cable formed as a cylinder around another. The current of one cable is exactly opposite that of the other. Each produces a magnetic field, but the fields cancel each other outside the outer cable. There is a very magnetic field between the cables. Because of the circular geometry, everything is symmetric. The inner cable is pulled outward in all directions, and the outer cable is pulled inward. After all is said and done, it works out to be a very useful and reliable piece of equipment.

Dr. Ken Mellendorf
Physics Instructor
Illinois Central College



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