Untitled Essay Research Paper INTRODUCTIONWe — страница 2

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 theory worked well for the conventional, metallic, low-temperature superconducting materials. But later on, new materials were discovered. It conducted at temperatures never before dreamed possible. That material was ceramic. What was believed to be an insulator became a superconductor. The latest Ceramic material discovered superconducts at 125 Kelvin. This is still far away from room temperature but now, liquid nitrogen could be used. It is much cheaper than the rare, expensive liquid Helium. Scientists still don’t know how the new superconductivity works. Some scientists have suggested that the new ceramics are new kinds of metals that carry

electrical charges, not via electrons, but through other charged particles.PROBLEMS / SOLUTIONS Throughout the time, scientists have succeeded in increasing the transition temperature which is the temperature required by a material to superconduct. Although they have reached temperatures much higher than 4k, it is still difficult to use superconductors in the industry because it is well below room temperature. Another problem is the fact that the new ceramic conductors are too fragile. They cannot be bent, twisted, stretched and machined. This makes them really useless. Scientists are attempting to find a solution to that by trying to develop composite wires. This means that the superconducting material would be covered by a coating of copper. If the ceramic loses its

superconductivity, the copper would take over until the superconductor bounced back. The old superconductors have no problem with being flexible but the required very low temperatures remain to be a problem. One good thing about ceramics is the fact that they generate extremely high magnetic fields. The old superconductors use to fail under low magnetic fields but the new ones seem to do well even with extremely high magnetic field applied on them.POSSIBLE USES The characteristics of a superconductor (low resistance and strong magnetic fields) seemed to have many uses. Highly efficient power generators; superpowerful magnets; computers that process data in a flash; supersensitive electronic devices for geophysical exploration and military surveillance; economic energy-storage

units; memory devices like centimetre-long video tapes with super conducting memory loops; high definition satellite television; highly accurate medical diagnostic equipment; smaller electric motors for ship propulsion; magnetically levitated trains; more efficient particle accelerators; fusion reactors that would generate cheap, clean power; and even electromagnetic launch vehicles and magnetic tunnels that could accelerate spacecraft to escape velocity.THE MAGNETICALLY LEVITATED TRAIN In my research, I had the chance to learn how two of these applications work: the magnetically levitated train and magnetically propelled ships. First, the magnetically levitated train, a fairly simple but brilliant concept. That train can reach great speeds since it had no friction with it’s

track. The guideway has thousands of electromagnets for levitation set in the floor along the way. More electromagnets for propulsion are set on the sides of the U-shaped track. The superconducting magnets on the train have the same polarity of the electromagnets of the track, so they push against each other and make the train float about 4 inches above ground. The interesting concept comes with propulsion. The operator sends and AC current through the electromagnets on the sides and can control the speed of the train by changing the frequency of the pulses. Supposing that the positive peak reaches the first electromagnet on the side of the track. That magnet will push the magnet making the train move forward. When the negative peak reaches that same magnet, the magnet on the