Physics 33.1 Surface Tension (6 of 12): Capillary Action: Example 1 (Water)

[@Galileosays]

Great explanation. It could be mentioned that the cosinus can be approximated yielding Rayleigh's formula: h+R/3=2 gamma / (rho g R).

[@MichelvanBiezen]

The mass of the liquid above the meniscus is very small compared to the mass of the rest of the liquid in the tube. Calculating the mass above the meniscus is more of a mathematical exercise than a practical endeavor.

[@冯孝伟]

I have a question, would the roughness of the glass bottle affect the hegiht to which water climbs up?

[@MichelvanBiezen]

Depends on how rough and if it has contaminats, etc. Yes, there will be some effect but rather minor.

[@zakirhussain-js9ku]

How does the system gain potential energy. What is energy equation to hold conservation law.

[@MichelvanBiezen]

The forces that pull the fluid up the tube are caused by the electrical forces of the charges in the atoms. The energy come from the charges being pulled out a bit from one another. (They act like little springs).

[@zakirhussain-js9ku]

@@MichelvanBiezen work has to be done to move charges.

[@MichelvanBiezen]

Yes, the energy will come from the attactive forces of the charges causing the positions of the charges to change a small amount.

[@ursulafiorelanavarro2074]

Hello professor, great video- I did an experiment with tween 80 in 20% solution but the final liquid level was lower than the reference... why might this happen?

[@MichelvanBiezen]

A lot of things can cause differences in recorded values, compared to expected value. There could have been a contaminant on the glass or in the solution. The diameter could be different than claimed, etc. What was the difference in the results? Also how did you deal with the meniscus?

[@ursulafiorelanavarro2074]

@@MichelvanBiezen can i please share it though your email address?

[@MichelvanBiezen]

Currently my schedule is very full. If you share it through these comments I may be able to take a look.

[@jonathanjanah3466]

thank you so much! you are just amazing, saving the day each time sine highschool physics all the way to my engineering degree!

[@MichelvanBiezen]

Glad you found our videos helpful 🙂

[@ahmedal-ebrashy3691]

14560 dynes/metre and divide by 1000kg/mcube divide again by 9.81m/secsqr divide again 0.0005m gives us 2968 metres or 2 km. So your answer sir was wrong. It will go of a height a bit above 2 kilometres

[@MichelvanBiezen]

The answer in the video is correct.

[@ahmedal-ebrashy3691]

Michel van Biezen I know, I was making fun at my own expense for my stupidity.

[@yellowridinghood1914]

is coefficient of surface tension a constant ? like is it always given in the question ?

[@MichelvanBiezen]

It is relativeley constant for water. It does depends on temperature, but we ignore that here for simplicity.

[@sarahsong1859]

Will the equation change is the tube is sealed and inclined???

[@vlad-adriananca7295]

What if you put a tube in, wich has a precise calculated diameter, and is curved at the top. Would the water rise and pour back creating a perpetuum mobile?

[@MichelvanBiezen]

From the laws of physics we know that is impossible. Using that as a guide, we can suspect that the liquid will rise to the top and not any farther.

[@iskandergussenov1880]

cos of theta cant be zero. You should take the angle between sloid, water and air. It is given by the curvature.

[@MichelvanBiezen]

You are correct, but he angle between glass and water is typically very close to zero degrees, and therefore cos(theta) ~ 1

[@dzul.fadliasraf]

The radius of the tube is one of the variables in this experiment. What about the surface area of the water in the beaker?? Does the surface area of water relates to the radius of the tube which cause it to pulled up the water??

[@MichelvanBiezen]

+Dzul Fadli Asraf The relevant factor here is the length of the surface (a.k.a the circumference of the inside of the tube)

[@phoenix7938]

Are these coefficients that you used based on the attractive forces between the fluid and glass specifically, or are they unrelated to the material that the capillary tube is made of? It would seem that if the coefficients are just based on the surface tension of a pure substance, not a substance in contact with another material, it would be difficult to apply these principles more broadly, say to a metal pipe.

[@MichelvanBiezen]

That is correct. There will be differences if different materials are used, however the differences tend to be small. The difference is typically seen in the "wetting angle" the angle the fluid makes with the surface, which is near zero for the water-glass boundary. (Not that for mercury the wetting angle is very different)

[@bensun5978]

my I know why there isn't obvious capillary action and effect in the "which tank fills up first experiment"?

[@MichelvanBiezen]

The effect of capillary action is only significant if the inside diameter of the tube is VERY small.

[@bensun5978]

Thank you!

[@1414gp]

sir what if two immiscible liquid are put in a container, where one of the liquid being wetting and other non-wetting

[@MichelvanBiezen]

+1414gp Which of the two liquids is on top? (They probably have different density)

[@1414gp]

+Michel van Biezen denser being at bottom . And is it important to know if wetting liquid is above or below

[@hamidhakim5385]

hi dr nice show im ask what is the surface tension value between sea water and glass ?

[@MichelvanBiezen]

It turns out it is about the same as the surface tension of pure water. (It does vary slightly with salinity and temperature).

[@prashanthkumar6871]

What is the formula in case of rectangular tube

[@alihosseiniroknabadi4828]

Thanks a lot; you're a great professor

[@MichelvanBiezen]

Just a simple man with all his faults, but glad we are able to help students.

[@punkinhaidmartin]

How will that work with oils an glycol like fluids?

[@MichelvanBiezen]

Mark, Good question. Every substance has a different coefficient. Some substances like Hg (mercury) act in an opposite fashion and actually depress in the tube instead of rise. You just need to look up the coefficient.

[@birhan2006]

mark warlick When using the formula to calculate h for different types of liquids and everything else being equal, use the proper surface tension/ density and be carful about cos angle, if it's greater than 90 you will get a negative h going down like mercury

[@Saddys1Away]

What the hell is a dyne

[@mlbbfannygameplay878]

1N=100000dynes =0.001KN

[@曾健能]

Doesn’t it has to change to si unit “N” before doing calculation?

[@AjaySharma-dl7uy]

Another reason to not use N

[@SubsonicDuck7]

fantastic explanation!! Thnx a lot..