I want to know the name or formula of any Material( compound or element ) which does not pass magnetic lines of forces through itself.neutrino - 30-10-2005 at 13:45
Try superconductors.pyrochem - 1-1-2006 at 09:21
You could try a diamagnetic substance such as bismuth or pyrolytic graphite. These substances repel magnets.sylla - 1-1-2006 at 14:24
Quote:
You could try a diamagnetic substance such as bismuth or pyrolytic graphite. These substances repel magnets.
That is because they create an inverse magnetic field.
Actually diamagnetic materials (that include supraconductors) have a relative permeability lower than 1 which means that any magnetic field
INSIDE the material will be smaller than the external magnetic field. But this relative permeability is close to one (water is 1 - 10e-5 !!!)
so it is hard to notice it. Supraconductors are exceptions to this, the effects can be seen. But I have never heard of any material that would have a
relative permeability of zero ! Even if it existed, the magnetic field would only be zeroed inside the material but will remain intact outside
("behind" the material).
To be honest, I think that a material that stops magnetic field cannot exists. Imagine a dot generating magnetic field. This is a dot that emits
splines that ends on the same dot. Now, draw a sphere around that dot. If you count all the outcoming lines going through that sphere it is equal to
the number of incoming lines through that same sphere. It does not only work with spheres but with any closed surface. This is mathematicaly
translated to "integral of B.dS on the closed surface S is null". This imply that divB is null too (Ostrogradski's Theorem). If magnetic lines where
killed outside that surface then there would be outgoing lines that don't come back so the integral isn't zero. That imply divB is not null too. And
that is a fucking problem because it is one of the great pillar of the electromagnetic wave equations. Modifying the property that divB is not always
zero would changes lots of thing in the world we know...
