Question

How is the capillary effect related to the contact angle?

Answer 1

Hint: Capillary action, also known as capillarity, capillary motion, or wicking, is a type of capillary action. The spontaneous flow of a liquid into a narrow tube or porous substance is defined as capillary action.

Complete step by step solution:
If you insert a fine straw into a glass of water, you'll notice that the water has risen above the straw and is now higher than the water level in the glass. By elevating the straw, it looks to have defied gravity. Capillary action is the term for this. This movement does not require the force of gravity to take place. It does, in fact, frequently defy gravity.

How plants, particularly the tallest shrubs, acquire water from their roots out to leaves and branches against the pull of gravity, is an example of capillary action. Capillary action is responsible. The practical implementation of the capillary can be seen in a variety of everyday situations. Water's capacity to pass through other materials is known as capillary action. It not only causes water to do this, but its qualities make it superior to most other substances in terms of wicking. As a result, jobs can be completed quickly and effectively.

The following equation describes the ascent of a liquid column in a capillary tube:
\[h = \dfrac{{2S\cos \theta }}{{r\rho g}}\]
Here, \[h\] is the height of the capillary tube, \[S\] is the surface tension of the fluid, \[\theta \] is the angle of contact, \[r\] is the radius of the capillary tube, \[\rho \] is the density of the liquid, and \[g\] is gravity.

If the angle of contact is less than \[90^\circ \], the value of \[\cos \theta \] is positive. And so, the value of \[h\] is also positive. As a result, the liquid rises in a capillary tube. If the contact angle is greater than \[90^\circ \] , the value of \[\cos \theta \] is negative, and so the value of \[h\] is negative as well. The liquid then drips into a capillary tube.

Note:When the radius of the meniscus remains constant, the height does not depend on the geometry of the capillary. The vertical height of a liquid column in capillaries of various sizes and shapes remains the same as a result of this.