发布时间： 2016年03月15日
概括大意与完成句子
1 A few countries are using powerful electromagnets to develop high-speed trains, called maglev trains. Maglev is short for magnetic levitation, which means that these trains float over a guide way using the basic principles of magnetic to replace the old steel wheel and track trains.
2 If you have ever played with magnets, you know that opposite poles attract and like poles repel each other. 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 battery. 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 tracks. The engine for maglev trains is rather unnoticeable. Instead of using fossil fuels, the magnetic field created by the electrified coils in the guide way walls and the track combines to propel the trains.
5 The magnetized coil running along the track, called a guide way, repels the large magnets on the train’s undercarriage, allowing the train to levitate between 1 to 10 cm above the guide way. Once the train is levitated, power is supplied to the coils within the guide way walls to create a unique system of magnetic fields that pull and push the train along the guide way. The electric current supplied to the coils in the guide way 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 500kph, or twice as fast as the fastest conventional train. At 500kph, you could travel from Paris to Rome in just over two hours.
1、Paragraph 3 _______
A、The Main Components of 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
【正确答案】 A
2、Paragraph 4 ______
A、The Main Components of 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
【正确答案】 E
3、Paragraph 5 ________
A、The Main Components of 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
【正确答案】 C
4、Paragraph 6 _________
A、The Main Components of 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
【正确答案】 B
5、Several countries in the world are using strong electromagnets ________.
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
【正确答案】 A
6、You can connect a wire to the positive and negative ends of a battery __________.
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
【正确答案】 D
7、A unique system of magnetic fields is created by the coils _______.
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
【正确答案】 C
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
【正确答案】 F
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