# Height of Meniscus

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1. Sep 18, 2016

### Cogsy

• Member advised to use the homework template for posts in the homework sections of PF.
I've been reading up on capillary action in a tube, and I have some questions:

1. Say we insert a tube in a pool of fluid; Jurin's Law expression is $h=\frac{2\sigma \cos \phi}{r\rho g}$. However, this height is not the height of the fluid measured from the bottom of the tube, but rather the difference in height produced by the capillary action. So, if a magical fluid had somehow no surface tension, there would be no height difference between the liquid inside the tube and the one outside of it, am I correct?
2. From which point in the meniscus do you measure said height? I've seen some authors draw the line up to the curved edge, others to the points where the meniscus makes contact with the tube, and some even do it in between. Also, does said point vary depending on whether the meniscus is concave or convex?

2. Sep 18, 2016

### Staff: Mentor

The idea is to determine the surface level of the fluid in the center of the container where it's essentially not influenced by the capillary action at the wall surface. So you read the lowest edge of the meniscus as viewed with your eye at the same level (for a concave meniscus).

The Wikipedia article on the meniscus has a reasonable overview.