职称英语考试备考辅导职称英语理工类教材概括大意新增部分

职称英语理工类教材概括大意新增部分(2)1A few countries are using powerful electromagnets to develop high-speed trains, called maglev trains. Maglev is short for magnetic levitation 1 , which means that these trains float over a guide way using the basic principles of magnets to replace the old steel wheel and track trains.2 If youve ever played with magnets, you know that opposite poles attract and like poles repel each other2. This is the basic principle behind electromagnetic propulsion. Electromagnets are similar to other magnets in that they attract metal objects, but the magnetic pull is temporary. You can easily create a small electromagnet yourself by connecting the ends of a copper wire to the positive and negative ends of an AA-cell battery3. This creates a small magnetic field. If you disconnect either end of the wire from the battery, the magnetic field is taken away.3The magnetic field created in this wire-and-battery experiment is the simple idea behind amaglev train rail system. There are three components to this system: A large electrical powersource, metal coils lining a guide way or track, and large guidance magnets attached to theunderside of the train.4The big difference between a maglev train and a conventional train is that maglev trains do not have an engine - at least not the kind of engine used to pull typical train cars along steel tracks4. The engine for maglev trains is rather innoticeable. Instead of using fossil fuels, the magnetic field created by the electrified coils in the guideway walls and the track combines to propel the trains5.5The magnetized coil running along the track, called a guideway, repels the large magnets on the trains undercarriage, allowing the train to levitate between 1 to cm above the guideway. Once the train is levitated, power is supplied to the coils within the guideway walls to create a unique system of magnetic fields that pull and push th train along the guideway. The electric current supplied to the coils in the guideway walls is constantly alternating to change the polarity of the magnetized coils. This change in polarity causes the magnetic field in front of the train to pull the vehicle forward, while the magnetic field behind the train adds more forward thrust.6Maglev trains float on a cushion of air, eliminating friction. This lack of friction allows these trains to reach unprecedented ground transportation speeds of more than 500 kph, or twice as fast as the fastest conventional train. At 500 kph, you could travel from Paris to Rome in just over two hours.词汇：Levitate v. 悬浮 electrified v. 使带电Levitation n. 悬浮 magnetize v. 使带磁guideway n. 导向槽 line v.排列成行propelb vt. 推进 underside n.下侧，下面propulsion n. 推进 undercarriage n. 车盘注释:1. Maglev is short for magnetic levitation :maglev 是 magnetic levitation 的缩略词。2. opposite poles attract and like poles repel each other: 异极相吸，同极相斥3. AA-cell battery:5号电池4. at least not the kind of engine used to pull typical train cars along steel tracks: 至少不是沿着轨道拉动典型的火车车厢的那种发动机。5. the magnetic field created by the electrified coils in the guideway walls and the track combine to propel the train: 由嵌入导向壁内的电磁线圈产生的磁场加上轨道，一起推动火车前进。The magnetic field 和 the track 是句子主语，created by the electrified coils in the guideway walls 是过去分词短语，用作定语，修饰the magnetic field.练习:1. Paragraph 32. Paragraph 43. Paragraph 5A The Main Components of the Maglev Train SystemB High-speed Maglev due to Zero FrictionC The Working Principle of the Maglev TrainD Differences between Polarity and Magnetic FieldE Comparison of Maglev Trains with Traditional OnesF Maglev with a Powerful Motor4. Paragraph 65. Several countries in the world are using strong electromagnets6. You can connect a wire to the positive and negative ends of a battery .7. A unique system of magnetic fields is created by the coils8. The frictionless maglev train enables youA to develop a maglev train rail systemB To explain why maglev trains are fasterC to pull and push the train forwardD to create a magnetic fieldE to experiment with the maglev trainF to travel from Paris to Rome in about two hours答案与题解：1. 第三段了举了磁浮列车的三个组成部分，动力源、金属线圈和此贴。选项A 概括了第三段列的内容。2. E 第四段就磁浮列车和传统火车进行了比较：磁浮列车没有发动机而传统火车有发动机。选项C用comparsion 来概括是准确的。3. C 第五段比较详细的介绍了为什么磁浮列车会向前运动，也就揭示了磁浮列车的工作原理。4. B 在第五段解释了磁浮列车浮起和向前运动的原理之后，在第六段中进行了磁浮列车速度奇快的原因：去除了传统火车的车轮于铁轨的摩擦。5. A 选A 的依据是本文第一段第一句：A few countries using powerful electromagnets to develop high-speed trains, called maglev trains.6.D第二段说，把电线与干电池相连接就能产生一个小磁场，而磁浮列车的运动原理与此相同。第二段第四句是选择D的依据。7. C第五段的第二句，即“0nce