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Tham khảo tài liệu 'anh ngữ sơ cấp - học tiếng anh bằng hình ành (phần 3) part 7', tài liệu phổ thông, tiếng anh phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | In many parts of the earth the climate is either too hot or too cold for man most of the year. But it is now possible to put automatic controls over temperature into houses offices and work plants. Here is a thermostat which keeps the temperature of the aữ as high or low as we want. We put the pointer at 70 F then the thermostat will keep the temperature of the room near 70 F the point on the scale to which the pointer points. climates weather through the year temperature amount of rainfall amount of water in the air and so on. thermostats Instrument for keeping automatic control over temperature pointer person or thing pointing. will point point s pointed 468 A thermostat is designed for this purpose. Its design makes use of our knowledge of what metals do when heated. low TEMPERATURE This is the way it works. HIGH TEMPERATURE Different metals get larger by different amounts as they are heated. Two long thin pieces of such different metals are bent together like this inside the thermostat. í í Í When the temperature in a room goes above 70 F metal on the outside gets longer than the metal on inside. This moves the arm to the right and shuts aS. fuel in the heating system of the house. for this purpose Io do this work. purpose o thing s purpose Is what It is designed to do. 469 When the room gets too cold the piece of metal on the outside gets shorter and moves the arm to the left. This turns on the heating system and more fuel is burned to warm the house. The purpose of putting a thermostat into a heating system is to control temperature. In hot climates what is important is to cool houses by sending fresh cold air through them. We can conưol the temperature of the rooms and in addition dry the air and have a climate of our own making indoors. Every ice chest has a climate of its own inside it. It is strange and surprising but true that ice chests are kept cold by using heat. The heat is supplied by electric power or by burning gas. Scientists tell us that before
