SUPERCONDUCTIVITY Essays - Superconductivity, Free Essays

SUPERCONDUCTIVITY Essays - Superconductivity, Free Essays SUPERCONDUCTIVITY The definition of superconductivity. Superconductivity is a phenomenon displayed by certain conductors that show no resistance to the flow of electric current. Conductors are materials in which the electron current goes through. There are 4 different kinds of conductors. Insulators, like glass or wood, have a very high resistance while semi-conductors, such as silicon, have a medium resistance. Conductors, like copper and other metals, have very low resistance, and superconductors, comprised of certain metals such as mercury and ceramics such as lanthanum-barium-copper-oxide, have no resistance. Resistance is an obstacle in the flow of electricity. Superconductors also have strong dimagnetism. In other words, they are repelled by magnetic fields. Due to these special characteristics of superconductors, no electrical energy is lost while flowing and since magnetic levitation above a superconductor is possible, new technology in the future could include high-speed trains that travel at 483 km/h (300 mph) while levitating on a cushion of air, powerful medical systems that have many more capabilities than the CAT scan, or even magnetically driven ships that get their power from the ocean itself (Gibilisco 1993, p 28). Making materials become superconductors. When superconductivity was first discovered, it was established that the compounds needed to be cooled to within several degrees Kelvin to absolute zero (zero Kelvin). Zero degrees Kelvin is the same as -460 degrees Fahrenheit and -273 degrees Celsius. The large amount of cooling was done by putting the compound in liquid helium. Helium, which is usually a gas, liquefies when its temperature drops to 4 K. Once the material had cooled to that temperature, it became a superconductor. However, using liquid helium to cool down material has been a problem. Liquid helium is very expensive, and the cooling equipment is very large (Langone 1989, p 8). In the past, there was no economic incentive to replace ordinary conductors with superconductors because the cooling costs for superconductors were so high. Scientists have tried to find ways to overcome the cooling problems, and so far they have found 2. The first is to find a way to cool the material using something less expensive and less bulky than liquid helium. The second way is to raise the temperatures that are necessary to cause superconductivity in the metals, or the critical temperatures. By combining materials into superconducting alloys, the temperature was raised slightly. By 1933, the critical temperature was at 10 K, and it wasn't until 1969 when the critical temperature was raised to 23 K and scientists tried, unsuccessfully, to raise it again. Then, in 1986, 2 IBM researchers in Zurich found a complex ceramic material that was superconducting at 30 K. After being increased to 39 K in late 1986, a critical temperature of 98 K was reported by Ching-WuChu and his research team at the University of Houston in 1987. A new coolant was then used. Liquid nitrogen liquefies at 77 K, is fairly inexpensive, and can even be carried around in a thermos (Mayo 1988, p 7). Liquid nitrogen costs about 50 cents a liter, while liquid h elium costs several dollars a liter. Thanks to this new discovery, efficient and cost-effective superconductors could be created. HISTORY OF THE SUPERCONDUCTOR Discovery. In 1911, the Dutch physicist Heike Kamerlingh Onnes discovered superconductivity while doing research on the effects of extremely cold temperatures on the properties of metals. While conducting his experiments, he discovered that mercury list all resistance to the flow of electricity when it was cooled to about 4 K. He then went on to discover superconductivity in other metals. In each case, the material had to be cooled to within several degrees Kelvin to absolute zero. To further his experiments, Onnes once put a current in a superconductor that was formed in the shape of a ring, and cooled it in liquid helium. One year after removing the source of electricity, the current was still flowing at its original strength in the superconductor (Hazen 1988, p 31). The only downside to the new finding was that scientists were unable to explain how it worked. Many scientists had theories, but it was Albert Einstein who perhaps summed it up best when he said in 1922, "With our cons iderable ignorance of complicated quantum-mechanical systems, we are far from

How to get Your CDL in Alabama, Arkansas and Mississippi

How to get Your CDL in Alabama, Arkansas and Mississippi This article is useful for anyone who wants to get a CDL in Alabama, Arkansas and Mississippi. If you want to learn about earning a CDL at other states, we have put together a comprehensive guide on how to get a commercial driver’s license in every state of the country. AlabamaBefore You Apply for Your CDL1. Get you  doctor to fill out  the current Department of Transportation Medical Examination Report (Form 649-F)2. Learn or review  the rules and regulations of commercial driving. You can study these in Alabama’s Commercial Driver License Manual.How to ApplyTake the following documents to your nearest Driver License Division office (make sure to research ahead for one that handles CDLs!):A current Alabama driver’s licenseA Social Security card or other proof of Social Security numberYour current DOT medical certificate (from above)Proof of insurance for the testing vehicle if you are taking the skills test$25 for the written test, $20 for the skills testL icense fees vary depending on your desired  class of license. Class A costs $66.25; Class B costs $56.25; Class Ccosts $36.25. If you are purchasing a CDL  or a license to operate only a school bus, the fee is $36.25.What to Expect When TestingFirst, on test day,  you will take one or more knowledge tests (which are written), depending on the license and endorsements you want.Then, if you pass the knowledge tests, you qualify to take the skills test (which is a driving test). Another option at this point is choosing to  be issued a learner’s license, which will allow you to practice driving  a rig with a licensed commercial driver in the passenger seat.When you feel   ready to take the on-road driving test, you can make another appointment at  the CDL licensing office.  The driving skills test includes: vehicle inspection (where you must  prove your vehicle’s safety and show your inspection skills), vehicle control (you will be asked to drive forward, backward, and in turns, in a small  area), and the actual driving test (this tests how well you know  Ã‚  signs, driving laws, and regulations).ArkansasBefore you take your certification exams, you must assess your driving record. If you have any serious offenses, like  DUI, you may be disqualified.The Knowledge TestsYou must pass the written knowledge test before you can take your road skills test. In order to familiarize yourself with the content of the exam, study the Arkansas  CDL Manual  to learn about driver safety, cargo safety, equipment, traffic rules, inspection procedures, and hazardous materials.To bring on test day:Documents that prove your age and identity$42, which is the fee for your CDLIf you haul hazardous materials, you will need to have federal  background and fingerprint check.The Road Skills TestAfter you have passed the written tests, you are ready for the road skills test.  On this test, you will be asked to perform driver tasks including pre-t rip inspections, changing lanes, tying down cargo, and maneuvering intersections.  The Arkansas CDL Manual review everything you will be tested on- review the criteria before test day so you are familiar with the tasks you will face.RequirementsYou must self-certify one of the following driving categories with the Arkansas DMV:Non-Excepted InterstateExcepted InterstateNon-Excepted IntrastateExcepted IntrastateIf you choose Non-Excepted Interstate, you must provide the DMV with a federal medical certificate.MississippiTo obtain a CDL in Mississippi, you must hold a  Regular Class R driver’s license. You must also obtain a current medical card when applying.Testing for the CDLNext stop is to take and pass the written and skills tests. All the information you need to know about the exam is in the Professional Driver’s Manual, which you can find at any  driver’s license office  throughout the state. You can schedule an appointment for the driving test either   online  or by phone.What You Must BringYour valid Mississippi driver’s license, a CDL learner’s permit, and your completed application for your desired CDLAnother driver to accompany you who holds the same class CDL license (or greater) as the one you seekA current medical cardThe same class of vehicle you will be driving once you obtain your CDL (it must pass inspection before any tests will be administered)A Social Security cardProof of residency (electric or water bill, lease agreement, vehicle-registration receipt, mortgage documents, homestead exemption receipt, bank statement, notarized employer verification on company letterhead (with a phone number) that states your address)Appropriate feesOut-of-state applicants applying for a Mississippi CDL can use their valid driver’s license from another stateNote: If your job entails hauling hazardous materials, you must undergo a background check. You will have to complete a  Driver’s License Hazard ous Materials Endorsement Application  and pay a fee.