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Correct definition of surface tension

  1. Mar 26, 2013 #1

    I have a question, because Im confused with the definition of surface tension.
    In my book it is defined as follows:
    "Surface tension is the energy required to increase the surface area of a liquid
    by a unit amount"

    What do they mean with increasing the surface area, how do you do that? If I take a glass with water it will look like this:

    I dont think there is any possible way to increase A. Can someone please help me out?

    Thanks in advance!
  2. jcsd
  3. Mar 26, 2013 #2


    User Avatar

    (A) in your diagram is a flat plane basically. Its surface area can be increased by pulling it upward or downward in the middle for example.

    The definition in your book is a little confusing because it is from a physics perspective and that is how surface tension is measured; force/length (N/m)

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