三、概括大意與完成句子
Maglev Trains
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.
詞匯：
Levitate v.懸浮 electrified v.使帶電
Levitation n.懸浮 magnetize v.使帶磁
guideway n.導(dǎo)向槽 line v.排列成行
propelb vt.推進(jìn) underside n.下側(cè)，下面
propulsion n.推進(jìn) undercarriage n.車盤(pán)
注釋：
1.Maglev is short for magnetic levitation:maglev 是 magnetic levitation 的縮略詞。
2.opposite poles attract and like poles repel each other:異極相吸，同極相斥
3.AA-cell battery:5號(hào)電池
4.at least not the kind of engine used to pull typical train cars along steel tracks:至少不是沿著軌道拉動(dòng)典型的火車車廂的那種發(fā)動(dòng)機(jī)。
5.the magnetic field created by the electrified coils in the guideway walls and the track combine to propel the train： 由嵌入導(dǎo)向壁內(nèi)的電磁線圈產(chǎn)生的磁場(chǎng)加上軌道，一起推動(dòng)火車前進(jìn)。The magnetic field 和 the track 是句子主語(yǔ)，created by the electrified coils in the guideway walls 是過(guò)去分詞短語(yǔ)，用作定語(yǔ)，修飾the magnetic field.
練習(xí)：
1.Paragraph 3
2.Paragraph 4
3.Paragraph 5
4.Paragraph 6
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
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
答案與題解：
1.A第三段了舉了磁浮列車的三個(gè)組成部分，動(dòng)力源、金屬線圈和此貼。選項(xiàng)A 概括了第三段列的內(nèi)容。
2.E第四段就磁浮列車和傳統(tǒng)火車進(jìn)行了比較：磁浮列車沒(méi)有發(fā)動(dòng)機(jī)而傳統(tǒng)火車有發(fā)動(dòng)機(jī)。選項(xiàng)C用comparsion 來(lái)概括是準(zhǔn)確的。
3.C第五段比較詳細(xì)的介紹了為什么磁浮列車會(huì)向前運(yùn)動(dòng)，也就揭示了磁浮列車的工作原理。
4.B在第五段解釋了磁浮列車浮起和向前運(yùn)動(dòng)的原理之后，作者在第六段中進(jìn)行了磁浮列車速度奇快的原因：去除了傳統(tǒng)火車的車輪于鐵軌的摩擦。
5.A選A 的依據(jù)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第二段說(shuō)，把電線與干電池相連接就能產(chǎn)生一個(gè)小磁場(chǎng)，而磁浮列車的運(yùn)動(dòng)原理與此相同。第二段第四句是選擇D的依據(jù)。
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”，是選擇c的依據(jù)。
8.F本文最后一句舉出坐上時(shí)速500公里的磁浮列車從巴黎到羅馬只需約2小時(shí)這個(gè)例子來(lái)說(shuō)明磁浮列車速度之快。
