can anything block magnitism?
Yes, you can shield against magnetic fields using any magnetic
material. One of the most effective shields is a material called
mu-metal. The idea is to 'trap' all the magnetic lines of force within
the metal and thus preventing it from affecting other objects in the
area. To be completely effective the shield should completely surround
the object you are trying to protect.
Electrical conductors attenuate a magnetig field. Superconductors exclude
a magnetic field entirely. That is the physical basis for "magnetic
levitation": magnetic fields actually repel superconductors.
Richard Barrans Jr., Ph.D.
you cannot really block magnetism, what "comes out" of a magnet (its
field lines, in our imaginary world) must go back in somewhere. BUT you
can redirect them with a magnetic material like soft iron. This is
commonly done. If there is some instrument or machine that is sensitive
to stray magnetic fields, even that of the earth, then that device can
be wrapped in soft iron (there is a thing called mu metal, just iron
really). It diverts the magnetic field away from the sensitive area.
Yes. Magnetic fields behave in much the same way as electric fields
at an interface between two materials, though the characteristic of the
materials that is important are different. For magnetic fields, the
important characteristic is the magnetic permeability, and a high-
permeability material like iron or mu-metal can be used to shield
against a magnetic field. A superconductor is an even better shield.
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Update: June 2012