discount mbt shoes A demonstration experiment on t

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A demonstration experiment on the improvement program

Jinsha County, Guizhou Province 551804 People's Education Publishing House of the eighth-grade physical materials (the book), the principle of the thermometer in the study, the design of a demonstration experiment: (see compulsory curriculum standard textbooks, eighth-grade physical volumes P76 demonstrates self thermometer). The reasonableness of this experimental program is worth discussion. Presentation made a number of thermometers installed in a small bottle with colored water, with a rubber stopper, rubber stopper on the inserted thin glass tube closed at one end, thin glass tube closed at one end to the heating, so that the air ran out of glass part quickly plugged with rubber stoppers bottle El. Will release the hot water bottle, small glass tube in the water column observed position, and then cold water then release the vial to observe the location of the water column. (Compulsory curriculum standard textbook, Figure 4.1-2 eighth grade physics book, P76 demo made thermometers) as shown in Figure I operate strictly in accordance with the experimental program, found that the experimental program a security risk and is not practical factors. Are as follows: First: Choose the glass tube closed at one end, in the course of the experiment there is a security risk. Our glass tube heated air inside the glass part to run away, the air becomes thin glass tube some, but there are still a lot of glass in the air. Then we plug the bottle with rubber stopper, when the temperature inside the glass tube and the outside temperature dropped to the same time, in the formation of a water column within a glass tube, and sealed glass tubes are also some air. When we put hot water bottle, small bottle of water expands when heated, so that the water column longer glass tube, sealed within the glass tube will lead to smaller gas volume,[link widoczny dla zalogowanych], pressure increases, resulting in a larger glass tube due to inability to afford the pressure instead. Serious threat to the safety of students and teachers. Second: If we choose a glass tube closed at one end of the closed end of the heating, open one end of the overflow tube of air is small. When we put on the hot water bottle,[link widoczny dla zalogowanych], bottle glass of water and into the formation of thermal expansion and contraction occurs when the water column, the length of the water column formed by the tube will be the impact of residual air. According to the nature of the gas we know: the quality of certain circumstances,[link widoczny dla zalogowanych], the smaller the size,[link widoczny dla zalogowanych], the greater the pressure; so gradually as the water bottle into the glass tube, glass tube will result in smaller air volume, pressure increases. Thus, in the case of low temperature,[link widoczny dla zalogowanych], air pressure inside the small glass tube, vial temperature is increased by l ° C, the increase in the water column within the tube should be longer; the temperature is high, the water column as a long glass tube, the volume of air inside the glass tube smaller pressure increases, the vial temperature is increased by l ° C, the increase in the water column within the tube should be shorter. Made in accordance with the principles of this thermometer, the scale should be uneven; while the actual use of the thermometer is uniform. Therefore chosen to explore the glass tube closed at one end is the principle of the thermometer unrealistic. Improved Methods: a glass tube open at both ends of the principles of inquiry is more appropriate thermometer. Choose a glass tube open at both ends to explore the principles of the thermometer, liquid column, and vials are subject to atmospheric pressure, atmospheric pressure liquid column, and vials by the offset. Therefore, the length of water column temperature controlled entirely by changes in, and exactly the same as the actual effect of the thermometer. Meanwhile, improved test program also can easily learn to use the Celsius thermometer made: the vial on ice the mixture long enough to remember the location of the water column and provide the representative there is 0 degrees Celsius temperature. Vial placed in boiling water and then a long enough time, note the location of the water column and provides the department on behalf of the temperature is 100 degrees Celsius. In this case, the change in the length of the water column is determined by the temperature, so changes in water column length is proportional to temperature. So we can put the water column between the two scale 100 equal portions, each decile is represented by l degrees Celsius. This can be achieved Celsius abstract concepts into visual image of the equally objective of the water column. Therefore, from safety point of view or from the realistic point of view, the time to explore the principles of the thermometer, choose a glass tube open at both ends of the glass tube open at one end than the choice is much more to the right. '
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