III. Find in the text and put down key words to speak about an alternator.

IV. Find words with similar meanings.

Current, size, to rotate, great, to move, flux, to vary, constant, fault, to revolve, power plant, to generate, to shift, to produce, to change, large, mistake, power station, volume, permanent.

V. Use the verbs given below to complete the text about a versatile device (Fig. 3).

charge shine charges turn listen turns produces

Fig. 3

Are you going on holiday? This 3-in-1 torch, radio and battery charger is for you.

When you the handle, it the dynamo. This the battery. You can then the torch, or to the radio. For example, five minutes at 120 rpm enough power to listen to the radio for twenty minutes. You can also turn the handle to your mobile phone.

VI. Match each of these terms with the correct description.

1. terminal 2. voltage 3. conductor 4. magnet 5. current	a) electrical force measured in volts
	b) the flow of electricity past a fixed point
	c) a piece of iron or steel which can make other metal objects come towards it either naturally or because of an electric current being passed through it
	d) a point at which connections can be made to an electric system
	e) something that acts as a path for electricity, heat, etc.

Text 4.

I. Read the text and write an outline for it.

Vocabulary

levitation [levɪˈteɪʃ ən] – левитация, поднятие

to float [fləut] – плавать, плыть

damper ['dæmpə] – амортизатор

suspension [sə'spenʃən] – подвеска

to maintain [meɪn'teɪn] – обслуживать

fiberglass ['faɪbəglɑ:s] – стекловолокно

chassis ['ʃæsɪ] – шасси

to exert [ɪg'zɜ:t] – приводить в действие; вызывать, создавать

linear ['lɪnɪə] – линейный

to shift – перемещать, передвигать

to eliminate[ɪ'lɪmɪneɪt] – устранять, исключать

layout ['leɪaut] – план, разработка

tolerance ['tɔlərəns] – допуск

feedback ['fi:dbæk] – обратная связь

The First Maglev Train

A maglev (magnetic levitation) train does not run along a track in the normal way. Instead, magnetic fields lift it above the track, so that the train “floats” along.

Because they have no wheels, axels, suspension, dampers, or brakes, maglev vehicles are light and compact. They are also pollution-free, as no fuel is burnt within the train, and cheap to maintain.

The world's first automated maglev system was a low-speed maglev shuttle (used in 1984–1995). It carried passengers from the terminal of Birmingham International Airport to the nearby railway station. The cars were made of lightweight fiberglass, carried on aluminium chassis.

All the electrical equipment which powered the cars was situated under the floors or the seats. Each car could take 32 passengers and their luggage, up to a weight of 3 tonnes. The trains traveled at a maximum speed of 42 km/h.

A concrete guideway above the ground supported a T-shaped track for the two-car maglev trains. The train represented electromagnetic suspension system (EMS). The maglev train was lifted from the track by magnetic attraction. This is the force by which two opposite magnetic poles attract each other (just as two of the same poles repel each other). Powerful electromagnets at each corner of the train exerted a pulling force which lifted the train upwards so that it floated 15 mm above the track.

As people got on and off, the weight of the train varied. It might drop closer to the track than the required 15 mm, or rose further from it. To keep it at an even distance from the track, the force was varied by a microprocessor.

The train was driven by an electric motor called a linear induction motor. Electromagnetic windings, or coils, on the train generated a magnetic field in which the magnetic poles shifted along the train. The field induced electric current in the track, which in turn generated its own magnetic field. The two fields in the track and the train interacted so that the shifting field pulled the floating train along the track.

Over the past few decades other maglev train systems were developed in Japan (JR-Maglev), and Germany (M-Bahn, Transrapid). The Transrapid system was used for the construction of the high-speed magnetic levitation line in Shanghai (China).

The major advantage of electromagnetic maglev systems is that they work at all speeds, unlike electrodynamic systems which only work at a minimum speed of about 30 km/h (19 mph). This eliminates the need for a separate low-speed suspension system, and can simplify the track layout as a result. On the downside, the dynamic instability of the system demands high tolerances of the track, which can offset, or eliminate this advantage. In practice, this problem was solved by improving the feedback systems, which allow to use close tolerances.