Here is the URL for another version of that magnetic
shielding article, with a bit more meat...shades of
Star Treks shields!!
http://www.cwru.edu/pubaff/univcomm/shield.htm
"The shielding completely contains magnetic fields as
large as 10,000 times the Earth's natural magnetic
field. Some of today's important technologies produce
fields this great and wreak havoc with the
identification codes on credit cards, wipe out
computer memories, and become a mini-radio station,
giving off a strong signal that interferes with
commercial television and radio stations.
Brown explains that a shielding coil is used again,
but the secondary and primary currents have to "dance"
together to achieve supershielding, where the opposing
coil currents cancel out the magnetic forces emitted.
He likens the results to a dam with a hole in it.
"Instead of plugging the hole with a finger to stop
the leakage, the dam can be discarded and the finger
holds everything back by itself," Brown says.
"We couldn't believe it when we first did the
mathematics. We found with a short and open outside
shield, we could get the same perfect suppression
obtained by an infinite shield," he adds. "We had a
zero magnetic field everywhere outside, even in those
regions where there was no secondary coil."
Trapping magnetic fields in a closed container
presents no problem, but to be able to trap them with
an open-coil system is what shocked the CWRU research
physicists. Shvartsman adds that every time they
describe the result to experts, the initial reaction
is disbelief.
The supershielding concept can also be applied to
electric fields. By turning the shielding around, it
can protect interior regions from an external field.
The magnetic and electric field shielding demands of
future technology may well be met by protective, but
open helmets of electric current and electric charges,
adds Brown. "With only partial screening, a magnetic
field system, as with Perseus in his Helmet of Hades,
can be made invisible to outsiders."
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