If you like to drink cocktails or other drinks from a straw, you probably noticed that when one of its ends is lowered into a liquid, the level of the drink in it is slightly higher than in a cup or glass. Why is this happening? Usually people don't think about it. But physicists have long managed to study such phenomena well and even gave them their own name - capillary phenomena. It's our turn to find out why this is happening and how this phenomenon is explained.
Why capillary phenomena occur
In nature, everything that happens has a reasonable explanation. If the liquid is wetting (for example, water in a plastic tube), it will rise up the tube, and if it is non-wetting (for example, mercury in a glass vial), then it will go down. Moreover, the smaller the radius of such a capillary, the higher the liquid will rise or fall. What explains such capillary phenomena? Physics says that they occur as a result of exposuresurface tension forces. If you look closely at the surface layer of the liquid in the capillary, you can see that in its shape it is a kind of circle. Along its border, the walls of the tube are subjected to pressure by the force of the so-called surface tension. Moreover, for a wetting liquid, its direction vector is directed downwards, and for a non-wetting liquid, it is directed upwards.
According to Newton's third law, it inevitably causes an opposing pressure equal in magnitude to it. It is this that causes the liquid to rise or fall in a narrow tube. This explains all kinds of capillary phenomena. However, for sure, many have already had a logical question: “And when will the rise or fall of the liquid stop?” This will happen when the force of gravity, or the Archimedes force, balances the force that makes the liquid move along the tube.
How can capillary phenomena be used?
One of the applications of this phenomenon, which has become widespread in the production of stationery, is familiar to almost every student or pupil. You probably already guessed that we are talking about a capillary pen.
Its device allows you to write in almost any position, and a thin and clear mark on paper has long made this subject very popular among the writing fraternity. Capillary phenomena are also widely used in agriculture to regulate movement and retain moisture in the soil. As you know, the land where they growculture, has a loose structure, in which there are narrow gaps between its individual particles. In fact, it is nothing but capillaries. Through them, water enters the root system and provides the plants with the necessary moisture and useful s alts. However, soil water also rises along these paths and evaporates rather quickly. To prevent this process, capillaries should be destroyed. Just for this, loosening the soil is carried out. And sometimes the reverse situation arises when it is necessary to increase the movement of water through the capillaries. In this case, the soil is rolled down, and due to this, the number of narrow channels increases. In everyday life, capillary phenomena are used under a variety of circumstances. The use of blotting paper, towels and napkins, the use of wicks in kerosene lamps and in technology - all this is possible due to the presence of long narrow channels in their composition.
