1 A 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 you've 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.
3 The magnetic field created in this wire-and-battery experiment is the simple idea behind a maglev train rail system. There are three components to this system: A large electrical power source, metal coils lining a guide way or track, and large guidance magnets attached to the underside of the train.
4 The 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.
5 The magnetized coil running along the track, called a guideway, repels the large magnets on the train's undercarriage, allowing the train to levitate between 1 to 10 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.
6 Maglev 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.
练习:
1. Paragraph 3
2. Paragraph 4
3. Paragraph 5
A The Main Components of the Maglev Train System
B High-speed Maglev due to Zero Friction
C The Working Principle of the Maglev Train
D Differences between Polarity and Magnetic Field
E Comparison of Maglev Trains with Traditional Ones
F Maglev with a Powerful Motor
4. Paragraph 6
5. Several countries in the world are using strong electromagnets
6. 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 coils
8. The frictionless maglev train enables you
A to develop a maglev train rail system
B To explain why maglev trains are faster
C to pull and push the train forward
D to create a magnetic field
E to experiment with the maglev train
F 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，作者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 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 the train along the guideway”，是选择c的依据。
8.F本文最后一句举出坐上时速500公里的磁浮列车从巴黎到罗马只需约2小时这个例子来说明磁浮列车速度之快。