. Practical physics. ch the contracting bubble is forcing out throughthe stem. Again, let a loop of fine thread be tied to a wire ring, as in Fig. the ring be dipped into a soap solution so as to form a film acrossit, and then let a hot wire be thrust through the film inside the tendency of the film outside the loop to contract will instantly snapout the thread into a perfect circle (Fig. 96). The reason that the threadtakes the circular form is that, since the film outside the loop is strivingto assume the smallest possible surface, the area inside the loop mustof course becom
. Practical physics. ch the contracting bubble is forcing out throughthe stem. Again, let a loop of fine thread be tied to a wire ring, as in Fig. the ring be dipped into a soap solution so as to form a film acrossit, and then let a hot wire be thrust through the film inside the tendency of the film outside the loop to contract will instantly snapout the thread into a perfect circle (Fig. 96). The reason that the threadtakes the circular form is that, since the film outside the loop is strivingto assume the smallest possible surface, the area inside the loop mustof course become as large as possible. The circle is the figure whichhas the largest possible area for a given perimeter. Let a soap film be formed across the mouth of a clean 2-inch funnel,as in Fig. 97. The tendency of the film to contract will be sufficientto lift its weight against the force of gravity. The tendency of a liquid to reduce its exposed surface to aminimum, that is, the toidoic// of a)it/ liquid surface to act like. Fig. 98. Some of the stages tlirougli which a slowly forming drop passes a stretched elastic membrane, is called surface totsion. The elas-tic nature of a film is illustrated in Fig. 98, which is from amotion-picture record of some of the stages through whicha slowly forming drop passes. 116. Ascension and depression of liquids in capillary was shown in Chapter II that, in general, a liquid standsat the same level in any number of communicating following experiments will sliow that this rule ceases tohold in the case of tubes of small diameter. MOLECULAR FORCES IN LIQUIDS 97 Let a series of cupillary tubes of diameter varying from 2 mm. mm. be arranged as in Fig. 99. When water or ink is poured into the vessel it will be found to risehigher in the tubes than in the vessel, and it will be seen that thesmaller the tube the greater the height to which itrises. If the water is re[)laced by mercury, however,the effects will be found to be just
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectphysics, bookyear1922
