Прочитайте текст и выполните задания Natural and synthetic polymers 1.With names such as polytetrafl...: ответ на тест 1077990 - Английский язык

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Natural and synthetic polymers
1.With names such as polytetrafluoroethyline and polyethyleneteraphthalate, it is not surpprising that polymers are usually called by by their more common name, plastic. But what, exactly, is a polymer or a plastic? Polymers are compounds made up of several elements that are chemically bound. Most compounds consist of large numbers of tiny molecules, which each contain just a few atoms. For example, a water molecule – H2O – contains two hydrogen atoms and one oxygen atom. But the molecules of polymers contain huge numbers of atoms, joined together in long chains.
2. Rubber, thanks to its many uses from rubber bands to car tyres, is one of the best-known polymers. It comes from latex, a natural liquid which comes from rubber trees. Rubber is therefore a natural polymer. However, most of the polymers used in industry are not natural, but synthetic. The term «plastic» is generally used to refer to synthetic polymers - in other words, those that are manmade.
3. Synthetic polymers can be divided into two main categories. Thermoplastics can be melted by heat, and formed in shaped containers called moulds. Thermosetting plastics, also called thermosets, can be heated and moulded like thermoplastics. They may also be mixed from cold ingredients. However; during cooling or mixing, a chemical reaction occurs, causing thermosets to cure. This means they set permanently, and cannot be moulded again. If a thermoset is heated after curing, it will burn.
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Why are polymers usually called plastic?

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Natural and synthetic polymers
1.With names such as polytetrafluoroethyline and polyethyleneteraphthalate, it is not surpprising that polymers are usually called by by their more common name, plastic. But what, exactly, is a polymer or a plastic? Polymers are compounds made up of several elements that are chemically bound. Most compounds consist of large numbers of tiny molecules, which each contain just a few atoms. For example, a water molecule – H2O – contains two hydrogen atoms and one oxygen atom. But the molecules of polymers contain huge numbers of atoms, joined together in long chains.
2. Rubber, thanks to its many uses from rubber bands to car tyres, is one of the best-known polymers. It comes from latex, a natural liquid which comes from rubber trees. Rubber is therefore a natural polymer. However, most of the polymers used in industry are not natural, but synthetic. The term «plastic» is generally used to refer to synthetic polymers - in other words, those that are manmade.
3. Synthetic polymers can be divided into two main categories. Thermoplastics can be melted by heat, and formed in shaped containers called moulds. Thermosetting plastics, also called thermosets, can be heated and moulded like thermoplastics. They may also be mixed from cold ingredients. However; during cooling or mixing, a chemical reaction occurs, causing thermosets to cure. This means they set permanently, and cannot be moulded again. If a thermoset is heated after curing, it will burn.
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Why are polymers usually called plastic?

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Engineers of the Imagination
1. U.S. physicist Richard Feynman first suggested the idea for nanomachines in 1959. He had given a lecture on the possibility of building devices atom by atom. Eric Drexler, another physicist, developed the idea. Beginning in 1977, Drexler wrote a series of books about nanoengineering. It was a great idea, but no one knew how to move individual atoms and put them in place. Engineers have not yet created practical nanomachines. They have developed micromachines. They have microscopic gears, wheels, and axles. These machines are no larger than a speck of dust.
2. Engineers at the U.S. Department of Energy’s Sandia National Laboratories in Albuquerque, New Mexico, have created a micromachine that has gears. Each one is smaller in diameter than a human hair. Making a tiny engine powerful enough to run one of these machines is a much more complicated problem. In 1988 engineers at the University of California – Berkeley created the world’s first micromotor. It was just 100 microns (100,000 nanometers) across. The motor was powered by static electricity. This energy made tiny gears spin at high speeds, but it wasn’t powerful enough to do any useful work.
3. Manufacturers may be able to produce these engines very cheaply, perhaps for only ten or fifteen dollars each. In 2003 Dr. Alex Zettl, a physicist at the University of California – Berkeley created the first nanomotor. It is a tiny electric motor so small that it can fit on the back of a cold virus. About two hundred of them could fit on a human hair. So far, all the motor can do is spin a tiny rotor. It has not produced enough power to run a machine. Engineers are certain, however, that they will soon develop much more powerful electric nanomotors.
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The Microwave oven
1. Shortly after the end of World War II, Percy Spencer, already known as an electronics genius and war hero, was touring one of his laboratories at the Raytheon Company. He stopped momentarily in front a magnetron, the power tube that drives a radar set. Feeling a sudden and strange sensation, Spencer noticed that the chocolate bar in his pocket had begun to melt.
2. Spencer, who obtained one hundred twenty patents in his lifetime, knew how to apply his curiosity. So he did what any good inventor would – he went for some popcorn. Spencer didn't feel like a snack, he asked for unpopped popcorn. Holding the bag of corn next to the magnetron, Spencer watched as the kernels exploded into puffy white morsels.
3. From this simple experiment, Spencer and Raytheon developed the microwave oven. The first microwave oven was very big and heavy. At first, it was used exclusively in restaurants, railroad cars and ocean liners – places where large quantities of food had to be cooked quickly. In fact, it took decades after the invention of the microwave oven for it to be refined to a point where it would be useful to the average consumer. Today, Percy Spencer's radar boxes melt chocolate and pop popcorn in millions of homes around the world.
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Solar towers
1) The need to develop renewable energy is widely seen as a futuristic technological challenge. In reality, some of the most effective ways of harnessing horsepower from nature are based on concepts that have existed for donkey’s years. The wind turbine is an obvious example. Another – less well known, but conceived almost a century ago – is the solar tower or solar chimney.
2) If the Australian company EnviroMission completes an ambitious solar tower project in the New South Wales desert, the technology could capture not just the sun's rays but the public's imagination worldwide, The firm is planning to construct a tower a colossal one kilometer high, if built, it will be the world's tallest structure by a huge margin.
3) How it works. A large glass enclosure is built, with a chimney at its centre. The sun heats the enclosure, causing expansion of the air inside. At the top of the chimney, the lower temperature and tower pressure due to the higher altitude create a pressure differential known as stack effect. This causes air to flow up the chimney. Electricity is generated by turbines at the bottom of the chimney, which are driven by the flow of air. The bigger the area of glass and the taller the chimney, the greater the airflow and the higher the generating capacity.
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Remote Control
1. The earliest example of remote control by radio waves was developed in 1898 by Nikola Tesla and described in his patent, named Method of an Apparatus for Controlling Mechanism of Moving Vehicle or Vehicles. In 1898, he demonstrated a radio-controlled boat to the public during an electrical exhibition. Tesla called his boat a «teleautomaton».
2. The first machines to be operated by remote control were used mainly for military purposes. Radio-controlled motor-boats, developed by the German navy, were used to ram enemy ships in WW I. Radio controlled bombs and other remote control weapons were used in WW II. Once the wars were over, the United States scientists experimented to find nonmilitary uses for the remote control. In the late 1940s automatic garage door openers were invented, and in the 1950s the first TV remote controls were used.
3. The first TV remote control, called «Lazy Bones», was developed in 1950 by Zenith Electronics Corporation (then known as Zenith Radio Corporation). «Lazy Bones» used a cable that ran from the TV set to the viewer. A motor in the TV set operated the tuner through the remote control. Although customers liked having remote control of their television, they complained that people tripped over the unsightly cable that meandered across the living room floor. Manufacturers used to only make remote controls that operated one TV set. However, they are now making universal remote controls that can operate any TV set. Experts predict that someday remote controls will control almost every device in the home.
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