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which material if any can block a magnetic field?
A theory if have thinking about requires two magnets opposed in charge to be close to each other however i need to isolate the charge of one of the magnets so that its field does not interfere with the area behind it.
Queen mary university of london, UK
If you could find a way to "isolate the charge" of a
magnet, I would be seriously impressed. This is because as far as
anyone knows, it's not possible. Magnetic charges (which are called
"poles") always comes in pairs (north and south). There are (as far as
we know) no such thing as magnetic monopoles: Every magnet you have
ever seen has both a north and a south pole.
As for blocking the
magnetic field itself, there are a couple of ways I can think of that
might work. The best (but hardest) way would be to use a superconductor
since magnetic fields cannot push their way though this. If this is
difficult to arrange, a simpler (but less effective) arrangement may be
to use an iron shield, which will tend to attract the magnetic field
into itself such that much less gets through to the "other side" (this
is how the "keeper" on a horse-shoe magnet works).
-Tamara & Mats
(republished on 07/13/06)
Follow-Up #1: magnetic monopoles and perpetual motion machines
reading the article about isolating a permanent magnet
and the answers,replies
I must say there are "magnetic" monopoles found.
so this is no longer a theory.
to find a way isolating an magnet would be wonderfull
because that way you could make a perpetum mobile
( = 2 magnets ontop of eachother with the northpole towards
eachother loosely / sliding fitted in a container,
stick a isolator inbewteen the 2 north poles and the top magnet will drop down remove the isolator and the magnets will push eachother apart, use the energy to move that isolator and the engine wil turn forever for free.
The recent hype about the discovery of 'magnetic monopoles' was misleading. The 'monopoles' were just the free ends of dipoles in an unusual condensed matter state. The net magnetic flux through a surface around the material was still zero, unlike for genuine fundamental monopoles.
Let's say, however, that genuine monopoles are found. That will have no bearing at all on the laws of thermodynamics. Perpetual motion machines will still be just as impossible as they are now. Even without monopoles, people often daydream about complicated schemes to get around the laws, but they never work.
(published on 09/21/09)
Follow-Up #2: expecting monopoles?
Physicists conclude that because magnetic field lines are circular they never diverge. It is this lack of divergence that leads to the Gauss' law of magnetism in Maxwell's equations.
div(B) = 0
With no divergence they conclude that there is no magnetic charge. Paul Dirac noticed in the 1930's that by introducing a magnetic charge the Maxwell's equations became fully symmetric.
The descriptions of electricity and magnetism suggest that they are symmetric and the question "Why is there no magnetic charge?" has been studied by many people ever since.
Here is some food for thought. Look at the flux lines for a dipole magnet:
Now, look at the flux lines between 2 electric charges:
Now, superimpose the electric flux lines over the magnetic. You will see that they match exactly! Some people have a hard time seeing the writing on the wall :-)
- Chad (age 32)
Dallas, TX, USA
Yes, the beautiful symmetry between magnetism and electricity does lead most of us to suspect that magnetic monopoles are a possibility. The conventional wisdom on this is that they are not easily created or destroyed under the current conditions of the universe. Those that were around earlier were enormously diluted during cosmic inflation, or perhaps somehow not compatible with an inflation-free cycle. So everyone would love to find some, but the odds don't look very good.
for some more information
(published on 10/06/09)
Follow-up on this answer.