Rise of a liquid in a capillary tube #science #class11physics #ephysics #hydroandfluid #neet
The rise of a liquid in a capillary tube is a phenomenon called capillary action. It is caused by the combination of two forces: surface tension and adhesion.
Surface tension is the property of liquid surfaces to act like stretched elastic membranes. It is caused by the attractive forces between the liquid molecules at the surface. Adhesion is the force of attraction between the liquid molecules and the molecules of the capillary tube material.
When a capillary tube is dipped into a liquid, the liquid rises up the tube until the weight of the liquid column is balanced by the force of surface tension acting on the meniscus (the curved surface of the liquid at the top of the column).
The height to which the liquid rises in the capillary tube is given by the following equation:
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h = 2T cos ฮธ / ฯgR
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where:
* T is the surface tension of the liquid
* ฮธ is the angle of contact between the liquid and the capillary tube material
* ฯ is the density of the liquid
* g is the acceleration due to gravity
* R is the radius of the capillary tube
The angle of contact is a measure of how well the liquid wets the capillary tube material. A small angle of contact indicates that the liquid wets the material well, while a large angle of contact indicates that the liquid does not wet the material well.
Capillary action is a very important phenomenon in nature and technology. It is responsible for the rise of water in plants, the movement of oil in lamp wicks, and the absorption of ink in blotting paper. It is also used in a variety of industrial applications, such as inkjet printing and microfluidic devices.
Examples of capillary action:
Plants: Water rises from the roots of a plant to the upper parts of the plant through capillary action. The xylem vessels in the plant stem act like capillary tubes, and the water is drawn up the vessels by the force of surface tension.
Lamp wicks:Oil rises up a lamp wick by capillary action. The cotton fibers in the wick act like capillary tubes, and the oil is drawn up the wick by the force of surface tension.
Blotting paper: Ink is absorbed by blotting paper by capillary action. The cellulose fibers in the blotting paper act like capillary tubes, and the ink is drawn into the paper by the force of surface tension.
Industrial applications of capillary action:
Inkjet printing:Inkjet printers use capillary action to deposit tiny droplets of ink onto paper.
Microfluidic devices: Microfluidic devices are tiny devices that use capillary action to manipulate fluids on a very small scale. Microfluidic devices are used in a variety of applications, such as medical diagnostics and drug discovery.
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