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Siphon in vacuum

  1. May 11, 2010 #1
    The Oxford dictionary is about to change its definition of a siphon to remove the reference to air pressure as being required. Will a siphon work in a vacuum?
     
  2. jcsd
  3. May 11, 2010 #2

    mgb_phys

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    No the water will boil.

    Although a siphon doesn't run on air pressure, air pressure still has an effect.
    The main limit on a siphon is that the head of water (the distance between the surface of the upper level and the top of the siphon hoop) can't be more than the height of a column of water supported by atmopsheric pressure (ie 9.8m)
    At lower pressures the maximum height of the loop will decrease and in vacuum it reaches 0
     
  4. May 11, 2010 #3
    I didn't say the liquid was water.
     
  5. May 13, 2010 #4

    mgb_phys

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    Doesn't matter - it will still have a finite vapour pressure.
    The mechanism of a siphon isn't air pressure - but you can't have a loop height more than the maximum column of the liquid that can be supported by air pressure.
     
  6. May 13, 2010 #5
    Last edited by a moderator: Apr 25, 2017
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