# Tagged Questions

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### When water climbs up a piece of paper, where is the energy coming from?

Take a glass of water and piece of toilet paper. If you keep the paper vertical, and touch the surface of the water with the tip of the paper, you can see the water being absorbed and climbing up the ...
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### How does a sponge “suck” up water against gravity?

If I take a sponge and place it in a shallow dish of water (i.e. water level is lower than height of sponge), it absorbs water until the sponge is wet, including a portion of the sponge above the ...
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### Why does string not wick down?

I regularly drink tea at work and I often reuse the tea bags (yes I know I'm a cheapskate). Yesterday afternoon I used a tea bag once and kept it in the cup in case I wanted another cup before I left....
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### Sandstone getting soaked with water

I have seen someone putting a sandstone in water. With only about 10% of the stone sitting in the water. One could see the stone getting soaked with water. So there must be a force, which lets the ...
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### What physical forces pull/press water upwards in vegetation?

Each spring enormous amounts of water rise up in trees and other vegetation. What causes this stream upwards? Edit: I was under the impression that capillary action is a key factor: the original ...
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### How is the water meniscus at the edge of a capillary tube

Suppose we have a capillary tube in which water can rise to a height of x cm. If we dip the tube such that the height above the surface is less than x, then how will the water meniscus be at the edge ...
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### Will a drop of liquid flow from from the wide opening to the narrow opening of a thin funnel by the effect of air pressure?

We have a funnel that is thin enough to keep a drop of liquid inside it as shown in this figure. Assuming that the funnel is placed on a horizontal table, will the drop flow from the left side to ...
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### Capillary action and conservation of energy [duplicate]

When I dip a paper towel in a cup of water the water gets drawn up due to capillary action. How is this reconciled with conservation of energy, as it would seem on the surface that the potential ...
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### How to move a bubble which is trapped by the capillary pressure?

I have a question about how to move a trapped bubble in a tube. If we assume to have a horizontal tube, with water on each side of the bubble. The point to the left of the bubble is point 1, while ...
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### How is sweating a pipe an example of capillary action?

I learned how to sweat a pipe today from my father. If you're not familiar with the process, this might help. One thing that jumps out at me is this line (from the above link, as well as my father's ...
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### How does a piece of paper manage to pump out the water from a bowl

When we go to bed at home, we started to put a bowl of water on the radiator (the air gets a bit dry). By instinct I put a soaked piece of paper (e.g. toilet paper) into the bowl and let it touch the ...
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### Bent capillary tube

What would happen if I bend a capillary tube and use it as shown in figure? 1.Will the water(or any other adhesive liquid) level remain same as before bending? 2.or it will come up till end? 3.Or ...
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### Size of a glass capillary for noticable capillary action

How big would a glass capillary have to be to have noticable capillary action? Also, does capillary action happen in plastic tubes?
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### Why does this capillary action generator not work?

So I was doing a bit of reading. Apparently the the obstacle to generating energy from the forces driving capillary action is breaking the surface tension at the top of a capillary tube. It is just ...
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### Equidistant coffee rings in a mug: pinning boundaries coupled with migration of solute or just sip volume?

I understand that you get coffee rings on a table as a result of solute migration (solutocapillarity) towards the pinning of the circumference of the coffee ring [Deegan et al.]. Below is an ...
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### Capillary tube of insufficient length

I was wondering if we have a very thin glass tube placed in a tub of liquid and the portion of the tube outside the liquid is lesser than the height to which the liquid can rise because of capillarity,...
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### Why do new towels dry better after a few uses?

Most of you will be familiar with the phenomenon: you have bought a new towel and you first have to wash it or use it a couple of times before it starts to work properly, i.e. dry your body after ...
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### Surface tension and capillarity

The cause of surface tension is said to be asymmetry in the forces experienced by the molecules at the surface due to different interactions with air and liquid, but then the same argument also ...
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### Surface tension and capillary rise

The expression for the height rise in a capillary tube is well known, and the surface tension of the liquid air interface is involved. But as I understand the adhesion force between the water and ...
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### Why does a paper towel absorb water upwards?

When I touch a paper towel to a drop of water I can see the water move upwards into the paper towel. What force is responsible for this gravity defying phenomenon?
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### Capillary action column height in a tube fitted inside another tube?

I was thinking about how would capillary action change in a tube (classic example) and in a tube fitted inside another tube (considering water as the liquid involved). Height of liquid column: where:...
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### Can capillary forces be used to make hydro electricity?

Could a device with very thin columns of glass or something that attracts water more be used to pull water up and then release it to drive generator and perhaps add vacuum. I have been wondering ...
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### Problem understanding the capillary action equation

As you know the equation of capillary action id given by: $h=\dfrac{2\gamma\cos\theta}{\rho gr}$ Where: $h$ is the height the liquid is lifted, $\gamma$ is the liquid-air surface ...
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### Capillaries in series

The velocity of fluid of viscosity $\eta$ through a capillary of radius $r$ and length $l$ at a distance $x$ from the center of the capillary is given by; $v=\frac{P}{4l \eta }(r^2-x^2)$ (where $P$ is ...
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### How does capillary action work in tubes which are closed at the top?

In all textbooks the examples and descriptions use tubes which are open at both ends. Our teacher remarked that if it were closed at one end like a test tube (albeit a thin one) even then capillary ...
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### Capillary action meniscus height in a tube fitted inside another tube?

I was thinking about how would capillary action change in a tube (classic example) and in a tube fitted inside another tube (considering water as the liquid involved). Height of liquid column: where:...
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### Capillary in a slanted tube with a bend

So I've read a question on here about Capillary action in a slanted tube, but my question goes a little further. Firstly though, could someone explain to me what is meant by the only answer to that ...
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### Capillary engine is impossible?

I read some articles saying that it is not obvious (or maybe impossible) to generate energy using capillary action. On the other hand in my understanding trees uses capillary action to extract water ...
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### percolation permeability threshold in Helium before and after lambda point transition

There's an experiment demonstrating the properties of super-fluid Helium compared to normal fluid Helium, in which the Helium is put in a jar who's bottom is porous. The super-fluid can pass through ...
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### The coffee ring effect

Would spin coating a homogeneous solution of colloids also result in a coffee ring structure? Or is it just naturally drop casted evaporation methods that lead to the same.
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### Capillary bridge force function given volume and distance

Given two surfaces and a fluidic glue with sufficient adhesion, what is the force provided by the capillary bridge provided the cohesive properties of the glue, volume, and distance between the ...
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### Surface tension & capillary action

While deriving the equation of height to which the fluid rises, we say that the surface tension pulls the water till the weight of water balances it, my doubt is that how can any force pull on ...
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### liquid trapped in wet sponge

If you soak a sponge in water, or some other liquid, and then let it hang then some liquid will flow down due to gravity but not all, some amount will remain trapped in the sponge by the capillary ...
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### Violation of conservation of energy… or not? [closed]

The work done by surface tension is double the increase in potential energy. This is a clear violation of conservation of energy. What is the flaw here? Work done by surface tension is \begin{align} ...
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### where does the energy for capillary action come from? [duplicate]

I think capillary action occurs because water molecules have a little magnetic field with poles so they can stack up on each other somewhat. When it happens though, where is the energy derived from to ...
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### Why don't we include the adhesive and cohesive force while calculating rise in a capillary tube?

The contact angle of a liquid solid interface is explained by saying that the liquid surface must be perpendicular to the resultant of adhesive cohesive and gravitational forces acting on it, since it ...
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### Can capilliary action move liquid against gravity?

I was wondering if it was at all possible to very slowly suck up water from a cup with a rope, and then deposit the water into another cup on a 3cm thick book or similar object. Here is an example ...
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### Ink in a pen on an artificial satellite

In an artificial satellite, a space traveler tries to fill a pen by dipping it in ink. The amount of ink filled in the pen as compared to the amount of ink filled on the Earth's surface will be: ...
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### How does this capillary-action setup not become a perpetual motion machine?

If you have a very thin glass tube and you place it into water, let's say the water in the tube rises to the height of $x$ mm from the surface of the water. What would happen if you poked a hole in ...
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### Irreducible liquid saturation preparation

When preparing a porous medium such as a rock to a "residual" or "irreducible" liquid (oil or water/brine) saturation, what is the best practice? The second fluid phase that fills the remainder of the ...
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### Indirect heating of a capillary

I'm planning to boil water in a capillary tube, but for that direct heating would not be possible (I guess) as it may melt the thin wall of the capillary, so I was thinking of indirect heating methods....
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### Contact Angle In Capillary

One Professor recently told me that in an insufficient length capillary, the contact angle doesn't change, its an inherent property which does not change. If the edges of capillary are extremely sharp ...
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### Flow Curve - Plotting Shear and Strain Rates at Different Pressures and Flow Rates in a Capillary

So I'm not really asking for a solution but more clarification on this type of problem since I'm kind of confused on the concept. So i have two capillaries of a different diameters and lengths. Im ...
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