| LEVITATION:
Well, most people from India and other parts of the world might have seen yogi's or magicians flying in air (see picture).Is it true???. Although there has been many stage shows of magicians demonstrating it, scientists do not believe so. They disclose these gimmicks as a big hoax!. |
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But scientists have proved that levitation is possible, although they haven't
achieved this yet with human beings. It is truly fascinating to watch an
object freely hovering in mid-air and, not surprisingly, levitation has
found its way into myths, science fiction and even politics . Leaving science
fiction aside,physics does know scores of different ways to levitate things.
For instance, a helicopter can be considered as a very impressive levitation
device that uses a stream of air to keep floating. Scientists have also
found many ways to levitate things without any noise or the need for petrol
or air, by using electromagnetic fields.
Today's science knows only one way to achieve REAL levitation, i.e. such that no energy input is required and the levitation can last forever. The real levitation makes use of diamagnetism , an intrinsic property of many materials referring to their ability to expel a portion, even if a minute one, of an external magnetic field. Electrons in such materials rearrange their orbits slightly so that they expel the external field. As a result, diamagnetic materials repel and are repelled by strong magnetic fields. |
| What is diamagnetism??
Diamagnetic substances have all their electrons paired up and are unaffected in a magnetic field eg. liquid nitrogen.The image of a high-temperature superconductor levitating above a magnet in fog of liquid nitrogen can hardly surprise anyone these days – it has become common knowledge that superconductors are ideal diamagnetics and magnetic field must expel them. |
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On the other hand, the enclosed photographs of water and a frog hovering
inside a magnet (not on board a spacecraft) are somewhat counterintuitive and will probably take many people (even physicists) by surprise. This is the first observation of magnetic levitation of living organisms as well as the first images of diamagnetics levitated in a normal, room-temperature environment (if we disregard the tale about Flying Coffin of Mohammed as such evidence, of course). |
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In fact, it is possible to levitate magnetically every material and every living creature on the earth due to the always present molecular magnetism. The molecular magnetism is very weak (millions times weaker than ferromagnetism) and usually remains unnoticed in everyday life, thereby producing the wrong impression that materials around us are mainly nonmagnetic. But they are all magnetic. It is just that magnetic fields required to levitate all these "nonmagnetic" materials have to be approximately 100 times larger than for the case of, say, superconductors. |
| As you might well know,
all matter in the universe consists of small particles called atoms and
each atom contains electrons that circle around a nucleus. This is how
the world is made. If one places an atom (or a large piece of a matter
containing billions and billions of atoms) in a magnetic field, electrons
doing their circles inside do not like this very much. They alter their
motion in such a way as to oppose this external influence. Incidentally,
this is the most general principle of Nature: whenever one tries to change
something settled and quiet, the reaction is always negative (you can easily
check out that this principle also applies to the interaction between you
and your parents). So, according to this principle, the disturbed electrons
create their own magnetic field and as a result the atoms behave as little
magnetic needles pointing in the direction opposite to the applied field.
As you probably saw many times when playing with magnets, magnets push
each other away if you try to bring together their like poles, for example,
two north or two south poles. Similarly, the north pole of the external
field will try to push away the “north poles” of magnetized atoms. Our
magnet creates a very large magnetic field (about 100 to 1000 times larger
than school or household magnets). In this field, all the atoms inside
the frog act as very small magnets creating a field of about 2 Gauss (although
very small, such a field can still be detected by a
Three basic schemes
using various aspects of diamagnetism allow the true levitation:
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| Superconductors are
ideal diamagnetics and
completely expel magnetic field at low temperatures. The picture shows a superconducting pallet levitating above a strong magnet. This levitation does not suffer any stability problems because the magnetic flux is pinned by defects in superconducting materials. For this fortuitous effect, superconductors can levitate even below a magnet. |
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| Superconducting levitation
is a very well known phenomenon and
not discussed further on this site. An object does not need to be superconducting to levitate. Normal things, even humans, can do it as well, if placed in a strong magnetic field. Although the majority of ordinary materials, such as wood or plastic, seem to be non-magnetic, they, too, expel a very small portion (0.00001) ofan applied magnetic field, i.e. exhibit very weak diamagnetism. Such materials can be levitated using magnetic fields of about 10 Tesla. For several decades, this levitation possibility had been in oblivion - even for experts in high magnetic fields - until we levitated a live frog in1996. |
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| Low temperatures (such
that air turns liquid) and
powerful magnets (such that cooking pans are drawn from a distance of several meters) are not what one is likely to have at home to be able to watch the superconducting or diamagnetic levitation. Engineers designing bearings in a motor or a disk drive are also unlikely to have ever considered levitating devices (magnetic bearings) that would require such conditions. Now, there is a way - at last - to have miniature levitating devices that even schoolchildren can make. As the picture shows, the real levitation is now at our fingertips. |
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"Parakkum rail"--Fastest
trains!!
Well these trains work on the theory of superconductivity. Basically they use the principle of magnetism. To put it very simple these trains work on the theory of superconductivity. |
| What is superconductivity??
When certain metals are cooled below a specific temperature,their electric resistance vanishes. This phenomenon is known as "superconductivity". Once current is applied to a coil made of superconductive metal, it continues to flow permanently and without loss. This coil can generate dozens of times stronger magnetic field than that of permanent magnets. For the Maglev, a bundle of extremely fine niobium-titanium alloy (superconductive metal) wire is embedded in a copper matrix in order to improve the stability of superconductivity. This wire is cooled with liquid helium (ca-269ßC) to be superconductive state. |
| How does train advance
forwards ?(Propulsion System)
By passing current through propulsion coils on the ground, a magnetic field (north and south poles) is produced, thus the train is propelled forward by the force fo attraction between opposite poles and the repulsive force of same poles acting between the ground coils and the superconducting magnets built into the vehicles. |
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How is it levitated
? (Levitation System)
When the superconducting magnets on the vehicles pass through at high speed current flows through levitation and guidance coils on the ground producing electrodynamic levitating force to the vehicles. |
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Why doesn't it collide
with the wall ?(Guidance System)
The levitation and guidance coils on either side are connected with electric power cables. They keep the vehicles in the center of the guideway at all times by exerting an attractive force on the further side of the vehicle and a repulsive force on the nearer side should the train move off center to either side. |
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I won't be doing any justice, if I don't mention the father of levitation..PROFESSOR
ERIC LAITHWAITE
Make a magnetic train yourself!!!!--Click here |
| ** All the above information
has been derived from various sources in the net. I do no take any credit
for any of these
materials. Links: Linear Chuo Shinkansen Nijmegan |