Magnetis Anhang
Sam-co-mag.: (= Samarium-Cobalt-Legierung).
[Geno Jezek]
The most popular legend: an elderly Cretan shepherd named Magnes was herding his sheep in an area of Northern Greece
called Magnesia, about 4.000 years ago.
Suddenly the nails in his shoes and the metal tip of his staff became
firmly stuck to the large, black rock on which he was standing. To find the
source of attraction
he dug up the Earth to find lodestones (load = lead or attract).
Lodestones contain magnetite, a natural magnetic material Fe3O4. This type of
rock was subsequently
named magnetite, after either Magnesia or Magnes
himself.
Greek & Chinese: The earliest discovery of the properties of
lodestone. Stories of magnetism date back to the first century B.C. in the
writings of Lucretius and Pliny
the Elder (23-79 AD Roman). Pliny wrote of a hill near the river Indus
that was made entirely of a stone that attracted iron. He mentioned the magical
powers of
magnetite. For many years following its discovery, magnetite (formed in oceans): was surrounded in superstition and was considered to possess
magical powers
(heal the sick, frighten away evil spirits and attract and dissolve
ships made of iron).
People believed that there were whole islands of a magnetic nature that
could attract ships by virtue of the iron nails used in their construction.
Ships thus disappeared
at sea were believed to have been mysteriously pulled by these islands.
Archimedes is purported to have used loadstones to remove nails from enemy
ships thus sinking
them. People soon realized that magnetite not only attracted objects
made of iron, but when made into the shape of a needle and floated on water,
magnetite always
pointed in a north-south direction creating a primitive compass. This
led to an alternative name for magnetite, that of lodestone or "leading
stone".
For many years following the discovery of lodestone magnetism was just a
curious natural phenomenon. The Chinese developed the mariner's compass some
4500 years
ago. The earliest mariner's compass comprised a splinter of loadstone
carefully floated on the surface tension of water.
[Peregrinus]
Credited with the first attempt to separate fact from superstition in
1269, wrote a letter describing everything that was known, at that time, about
magnetite.
It is said that he did this while standing guard outside the walls of Lucera which was under siege. While people were starving to
death inside the walls, Peter Peregrinus
was outside writing one of the first 'scientific' reports and one that
was to have a vast impact on the world.
[William Gilbert]
In 1600 in the understanding of magnetism. It was Gilbert who first
realized that the Earth was a giant magnet and that magnets could be made by
beating wrought iron.
He also discovered that heating resulted in the loss of induced
magnetism.
[Oersted & Maxwell]
In 1820 Hans Christian Oersted (1777-1851
Danish) demonstrated that magnetism was related to electricity by bringing a
wire carrying an electric current close to a magnetic compass which caused a
deflection of the compass needle. It is now known that whenever current flows
there will be an associated magnetic field in the surrounding space,
or more generally that the movement of any charged particle will produce
a magnetic field.
James Clerk Maxwell (1831-1879 Scottland):
established beyond doubt the inter-relationships between electricity and
magnetism and promulgated a series of deceptively simple equations that are the
basis of electromagnetic theory today. What is more remarkable is that Maxwell
developed his ideas in 1862 more than thirty years before
J. Thomson discovered the electron in 1897, the particle that is so
fundamental to the current understanding of both electricity and magnetism.
The term magnetism was thus coined to explain the phenomenon whereby
lodestones attracted iron. Today, after hundreds of years of research we not
only know the attractive and repulsive nature of magnets, but also understand
MIR scans in the field of medicine, computers chips, television and telephones
in electronics and even that certain birds, butterflies and other insects have
a magnetic sense of direction. A magnet is an object with a magnetic field. It
attracts ferrous objects (pieces of iron/steel/nickel/cobalt).
The Greeks observed that the naturally occurring 'lodestone' attracted
iron pieces.
These days magnets are made artificially in various shapes and sizes
depending on their use. One of the most common magnets (the bar magnet) is a
long, rectangular bar of uniform cross-section that attracts pieces of ferrous
objects.
The end of a freely pivoted magnet will always point in the N.-S.
direction.
The end that points in the North is called the North Pole of the magnet
and the end that points South is called the South Pole of the magnet. It has
been proven by experiments that like magnetic poles repel each other whereas
unlike poles attract each other. Correctly matched poles create the tight
magnetic attraction that is commonly understood.
Magnetic Fields
What is a magnetic field? The space surrounding a magnet, in which
magnetic force is exerted, is called a magnetic field. If a bar magnet is
placed in such a field, it will experience magnetic forces. However, the field
will continue to exist even if the magnet is removed. The direction of magnetic
field at a point is the direction of the resultant force acting on a
hypothetical N. Pole placed at that point.
How is a magnetic field created?
When current flows in a wire, a magnetic field is created around the
wire. From this it has been inferred that magnetic fields are produced by the
motion of electrical charges. A magnetic field of a bar magnet results from the
motion of negatively charged electrons in the magnet.
Just as an electric field is described by drawing the electric lines of
force, in the same way, a magnetic field is described by drawing the magnetic
lines of force. When a small north magnetic pole is placed in the magnetic
field created by a magnet, it will experience a force. And if the North Pole is
free, it will move under the influence of magnetic field. The path traced by a
North magnetic pole free to move under the influence of a magnetic field is
called a magnetic line of force. In other words, the magnetic lines of force
are the lines drawn in a magnetic field along which a north magnetic pole would
move.
The direction of a magnetic line of force at any point gives the
direction of the magnetic force on a north pole placed at that point. Since the
direction of magnetic line of force is the direction of force on a North Pole,
so the magnetic lines of force always begin on the N-pole of a magnet and end
on the S-pole of the magnet. A small magnetic compass when moved along a line
of force always sets itself along the line tangential to it. So, a line drawn
from the South Pole of the compass to its North Pole indicates the direction of
the magnetic field.
Properties of the magnetic lines of
force
The magnetic lines of force originate from the North Pole of a magnet
and end at its South Pole.
The magnetic lines of force come closer to one another near the poles of
a magnet but they are widely separated at other places.
The magnetic lines of force do not intersect (or cross) one another.
When a magnetic compass is placed at different points on a magnetic line
of force, it aligns itself along the tangent to the line of force at that
point.
The Largest Magnets
The Earth itself is a magnet! Researchers think it’s the effect of
convection currents in our planet’s molten interior causing the entire Earth to
behave as one gigantic magnet, with a n. and s. pole. Whenever you look at a
compass, what you’re doing is reading the magnetic field of the planet on which
you are standing. But even a magnet the size of a planet can’t compete with a
magnet the size of a star.
For example, the sun is a magnet. In this case, the magnetic field is
probably generated by swirling plasma. Magnetic storms on the sun are powerful
enough to have an effect on satellites and communication systems all the way
here on Earth. Still, there are things
in space that put all of these magnets to shame.
Time-Space Distortion
Electric charges and magnets do indeed "distort space," but
this happens on a couple of levels.
According to the current best theory of gravitation, which is contained
in Albert Einstein's famous general theory of relativity, a
gravitational field represents a curvature of space-time, rather than a
distortion of it.
Anything that carries energy, momentum and stresses is a source of a
gravitational field, that is, a curvature of space-time.
Electric charges and magnets are manifestations of certain types of
matter, most particularly electrons. Since matter carries energy (via
Einstein's famous relation that energy is mass times the speed of light
squared), such objects will have a gravitational field and so they will distort
space-time. So one way in which a charge or a magnet will distort space-time is
by virtue of its matter.
You see, electromagnetic fields themselves carry energy (and momentum
and stresses. Because an electromagnetic field contains energy, momentum, and
so on, it will produce a gravitational field of its own. This gravitational
field is in addition to that produced by the matter of the charge or magnet.
This Time-Space distortion is based on the same principle that distorts
time and space around a Black Hole” in space.
Rare Earth Minerals (Lanthanides)
As defined by IUPAC, rare earth elements or rare earth metals are a set
of 17 chemical elements in the periodic table (15 lanthanides plus scandium and
yttrium).
Scandium and yttrium are considered rare earth elements since they tend
to occur in the same ore deposits as the lanthanides and exhibit similar
chemical properties.
Despite their name, rare earth elements (with the exception of the
radioactive promethium) are relatively plentiful in the Earth's crust, with
cerium being the 25th most abundant element at 68 parts per million (similar to
copper). However, because of their geochemical properties, rare earth elements
are typically dispersed and not often found in concentrated and economically
exploitable forms. The few economically exploitable deposits are known as rare
earth minerals. It was the very scarcity of these minerals (previously called
"earths") that led to the term "rare earth". The first such
mineral discovered was gadolinite, a compound of cerium, yttrium, iron, silicon
and other elements.
Rare Earth Minerals in Green Earth
Technology
Numbers 57 through 71, along with number 37, of the periodic table of
elements are collective known as the rare earth minerals. These particular
elements are garnering a lot of attention these days due to the well-known
problems which are rising from our dependence as a society on fossil fuels.
These particular elements of the periodic table hold great promise for
unlocking new sources of green energy.
Rare earth minerals have the potential to revolution the way a car
works, because they can play a major role in the functioning of hybrid electric
vehicles. The technology involved here
is called the "rare earth permanent magnet." This device works by
stimulating the flow of electrons from one atom to another and by doing so, it
can generate a substantial amount of electrical energy. These electric traction
drives can supplement or even totally replace the internal combustion engine,
thus doing away to a significant extent or even entirely with the need to burn
fossil fuels in order to make your car run. In short, the possibilities lurking
in rare earth minerals for green technologies is immense.
Rare Earth Magnets
Rare-earth magnets are strong permanent magnets made from alloys of rare
earth elements. Developed in the 1970s and 80s, rare-earth magnets are the
strongest type of permanent magnets made and have significant performance
advantages over ferrite or alnico magnets. The magnetic field typically
produced by rare-earth magnets can be in excess of 1.4 teslas,
whereas ferrite or ceramic magnets typically exhibit fields of 0.5 to 1 tesla.
2 types: neodymium magnets and samarium-cobalt magnets. Rare earth
magnets are extremely brittle and also vulnerable to corrosion, so they are
usually plated or coated to protect them from breaking and chipping.
Rare Earth Mining In
China
Why aren’t there more companies mining them? Rare earth minerals are not
something new. They have been mined in the past but the process of mining them
was too expensive to make it worthwhile since the applications for these
minerals were minimal. Today, the demand is there and unfortunately, there are
simply not many mines active. This leads to the underlying problem in supply.
Rare earth minerals are those found within the earth that until recent
decades, have not been thought of as valuable. Many companies stopped mining
for these products because of the limited use of them, and the fact is where
there is limited use, there are also limited funds. However, new technologies
found the exceptional benefits of these minerals for commercial, defense, and everyday technologies. Since then, demand has
greatly increased, so the minerals are considered “rare” because there’s not
enough being mined to fit demand. China continued to mine and so is really the
only one mining at the level necessary for the demand present.
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