Untitled Essay Research Paper INTRODUCTIONWe

Untitled Essay, Research Paper

INTRODUCTION

We’ve all heard about superconductivity. But, do we all know what it

is. How it works and what are its uses. To start talking about

superconductivity, we must try to understand the how "normal" conductivity

works. This will make it much easier to understand how the "super" part

functions. In the following paragraphs, I will explain how superconductivity

works, some of the current problems and some examples of its uses.CONDUCTIVITY

Conductivity is the ability of a substance to carry electricity. Some

substances like copper, aluminium, silver and gold do it very well. They are

called conductors. Others conduct electricity partially and they are called

semi-conductors. The concept of electric transmission is very simple to

understand. The wire that conducts the electric current is made of atoms

which have equal numbers of protons and electrons making the atoms

electrically neutral. If this balance is disturbed by gain or loss of electrons,

the atoms will become electrically charged and are called ions. Electrons

occupy energy states. Each level requires a certain amount of energy. For an

electron to move to a higher level, it will require the right amount of energy.

Electrons can move between different levels and between different materials

but to do that, they require the right amount of energy and an "empty" slot in

the band they enter. The metallic conductors have a lot of these slots and

this is where the free electrons will head when voltage (energy) is applied. A

simpler way to look at this is to think of atoms aligned in a straight line (wire).

if we add an electron to the first atom of the line, that atom would have an

excess of electrons so it releases an other electron which will go to the

second atom and the process repeats again and again until an electron pops

out from the end of the wire. We can then say that conduction of an electrical

current is simply electrons moving from one empty slot to another in the

atoms’ outer shells.

The problem with these conductors is the fact that they do not let all

the current get through. Whenever an electric current flows, it encounters

some resistance, which changes the electrical energy into heat. This is what

causes the wires to heat. The conductors become themselves like a

resistance but an unwanted one. This explains why only 95% of the power

generated by an AC generator reaches consumers. The rest is converted

into useless heat along the way. The conducting wire is made of vibrating

atoms called lattice. The higher the temperature, the more the lattice shakes

making it harder for the electrons to travel through that wire. It becomes like

a jungle full of obstacles. Some of the electrons will bump with the vibrating

atoms and impurities and fly off in all directions and lose energy in form of

heat. This is known as friction. This is where superconductivity comes into

work. Inside a superconductor, the lattice and the impurities are still there,

but their state is much different from that of an ordinary conductor.SUPERCONDUCTIVITY (Theory / history)

Superconductivity was discovered in 1911 by Heike Kamerlingh

Onnes, a Dutch physicist. It is the ability to conduct electricity without

resistance and without loss. At that time, it took liquid helium to get extremely

low temperatures to make a substance superconduct, around 4 kelvins. That

wasn’t very far from absolute Zero (The theoretical temperature at which the

atoms and molecules of a substance lose all of their frantic heat-dependent

energy and at which all resistance stops short.) Kelvin believed that electrons

travelling in a conductor would come to a complete stop as the temperature

got close to absolute zero. But others were not so sure. Kelvin was wrong.

The colder it gets, the less the lattice shakes, making it easier for electrons

to get through. There’s one theory that explains best what happens in a

superconducting wire: When a conductor is cooled to super low

temperatures, the electrons travelling inside it would join up in some way and

move as a team. The problem with this notion was that electrons carry

negative charges and like charges repel. This repulsion would prevent the

electrons from forming their team. The answer to that was phonons. It is

believed that packets of sound waves (phonons) that are emitted by the

vibrating lattice overcome the electrons natural repulsion making it possible

for them to travel in team. It’s as if they were all holding hands together. If

one of them falls in a hole or bumps into something, the preceding electron

would pull him and the following one would push. There was no chance of

getting lost. Since the lattice was cooled, there was less vibration making it

easier for the paired electrons to go through.NEW MATERIAL

That the

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