Capillary effects

When hydrostatics just doesn’t explain things.

Occasionally one notices water levels in straws that are slightly above the water levels in the glass. And of course – even though we always talk about water seeking its level and hydrostatics and stuff – we know that that’s how it should be because of the capillary effects. And then we probably all did that experiment in school where we had a very thin glass tube and the water rose really really high.┬áBut have you ever wondered how heights between straws with different diameters would differ? (Really? Only me?)

Anyway, here is how:

I do realize that the diameter of “typical” straws differs from country to country, but these are the Norwegian – and German – typical straws, so I herewith define this as universally typical. Anyway, from left to right: 8mm, 4mm and 3mm diameter on the outside. Unfortunately I don’t have the tools to measure the inner diameter. Plus I really need to get clear thin straws! Sorry the water level is so hard to see in the yellow straw – I even dyed the water for you!

But even with the imperfect materials I have – isn’t this quite an impressive result?

Btw, this is what it looked like when I did the experiment in my kitchen.

When in doubt, pile higher. And deeper.

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