What are the capillary phenomena and how are they explained?

If you like drinking cocktails or other drinks from a tube, you probably noticed that when one of its ends is lowered into the liquid, the level of the drink in it is slightly higher than in a cup or glass. Why is this happening? Usually people do not think about it. But physicists like these phenomena have long had time to study well and even gave them their own name - capillary phenomena. It's also our turn to find out why this happens and how this phenomenon is explained.

Why do 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 go up the tube, and if it is not soaking (for example, mercury in a glass cone), then go down. And the smaller the radius of such a capillary, the higher the liquid rises or falls. What explains such capillary phenomena? Physics says that they occur as a result of the influence of surface tension forces. If you look closely at the surface layer of liquid in the capillary, you can see that in its form it represents a certain circle. Along its boundary, the force of the so-called surface tension exerts pressure on the walls of the tube. Moreover, for the wetting liquid the vector of its direction is turned downward, and for non-wetting liquid it is turned upwards. According to Newton's third law, it inevitably causes an opposing pressure equal to it in modulus. It just makes the liquid rise or fall in a narrow tube. This explains all kinds of capillary phenomena. However, for sure, many already had a logical question: "And when will the lifting or lowering of the liquid stop?" This will happen in the case when the gravity force, or the Archimedes force, will balance the force that causes the liquid to move along the tube.

How can I use capillary phenomena?

With one of the applications of this phenomenon, which has become widespread in the production of stationery, virtually every student or student is familiar. You probably already guessed that it was a capillary pen.
Her device allows you to write in almost any position, and a thin and clear trace 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 crops are grown has a loose structure, in which narrow gaps exist between its individual particles. In fact, it is nothing but a capillary. On them water comes to the root system and provides plants with the necessary moisture and useful salts. However, along these paths, the soil water also rises and quickly evaporates. To prevent this process, you must destroy the capillaries. Just for this purpose, loosening of the soil is carried out. And sometimes there is a reverse situation, when it is required to increase the movement of water through the capillaries. In this case, the ground is rolled out, and due to this the number of narrow channels increases. In everyday life, capillary phenomena are used in a variety of circumstances. 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 in their composition of narrow long channels.