# Untitled Essay Research Paper INTRODUCTIONWe

• Просмотров 212
• Скачиваний 5
• Размер файла 17
Кб
﻿
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

• Рефераты