第1个回答 2012-08-11
A Train Floating On Air
A train that floats on air? It' s not magic — it' s magnets（磁）．And it' s close to reality．
In Virginia USA the fall of 2002, a train with no wheels traveled on air and carried college students across their campus．In Japan, a whisper - quiet railway engine hovered and raced at 350 miles per hour using magnets and electricity as the power．And in China, a magnet train line linked Shanghai with nearby Pudong Airport．
These trains use magnetic levitation（悬浮）technology, "maglev" for short．They use the same rules as the magnets you pick up at home or school: opposite poles of magnets attract each other, and like poles repel each other．
How does it work?
Powerful magnets on the bottom of the train repel magnets on the track, which is actually just a magnet - filled guiding way. With a magnetic field of sufficient force, the train will go hovering on air, which seemed impossible to us in the past．
When an electrical current is sent through the track, the train moves．Turn the current backwards and the train slows down．
Maglev doesn't rely on the friction（摩擦力）of wheels on track, so it can climb a much steeper hill than a traditional train．And it can travel easily in snow and ice, something that could bring normal trains to a screaming stop．
49．This passage is about ．
A．maglev B．magnets C．levitation D．electricity
50．Which of the following is a repelling action?
51．What can we learn from the text?
A．A magnet - filled guiding way is formed inside a maglev train．
B．Instead of electricity, magnets are used as the power of a maglev．
C．Maglev trains can climb hills with the help of magnet wheels．
D．Electric currents decide the movements of a maglev train．
52．What is the difference between a maglev train and an ordinary train?
A．.A maglev train can climb mountains without power while an ordinary one can' t．
B．A maglev train can travel in college campus while an ordinary train is not allowed．
C．Travelling without a track, a maglev train is safer and smoother than an ordinary one．
D．Floating on a track, a maglev train is faster, quieter than an ordinary railway train．
我帮你百度的，不知道是不是你想要的。。。