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: 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 that 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.

 

 

Vorwort/Suchen                                Zeichen/Abkürzungen                                   Impressum