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B Capillary action with Mercury

  1. Jul 27, 2018 #1
    It's a question which come into my mind after reading related notes now and again and I can't think of plausible response to it.
    Given Statements:
    We have a container filled with mercury and a glass capillary tube placed in it . As tube's diameter become smaller mercury's height in tube will get shorter and shorter.The reason said to be due to strong cohesion mercury has which makes it reluctant to stick to capillary walls and go higher unlike water.
    My Question:
    If mercury has such strong cohesion why it's seen to rise,although small, in our glass tube?

    I'll appreciate any help !
  2. jcsd
  3. Jul 27, 2018 #2


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  4. Jul 27, 2018 #3
    Well it's right but why it's not totally getting out of tube?
  5. Jul 28, 2018 #4


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    The resultant of its cohesive forces and the forces adhering to the glass has a downwards component which acts against the force due to the hydrostatic pressure of the liquid. Net result is a lower level. The mercury is pulled downwards.
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