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How effective is torricellian vaccum?

  1. Jul 24, 2012 #1
    i have designed a vaccum "pump" which uses torricellian vaccum.my "pump" just increases the size of torricellian vaccum by creating a low pressure area outside the barometer like apparatus.but that's not the question.my question is,how effective,or absolute is torricellian vaccum?is it complete vaccum,or does it still have some particles floating around?if i were to make a cathode ray tube like this,would it work?
     
  2. jcsd
  3. Jul 24, 2012 #2

    Drakkith

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    Staff: Mentor

    Practically all man made vacuums will have at least some residual particles floating around. I don't know how effective your vacuum is though, sorry.
     
  4. Jul 24, 2012 #3
    The pressure above the mercury surface will be the vapour pressure of mercury which is about 1.2μmm.Hg
     
  5. Jul 24, 2012 #4
    The torricellian vacuum is limited by the vapor pressure of the liquid that you use to make the vacuum. Whatever liquid you use will have a specific vapor pressure at the temperature of the liquid.
    When the vacuum finally reaches equilibrium, the pressure inside the cavity will equal the vapor pressure of the liquid. The particles in the partial vacuum will be molecules of vapor from the liquid.
     
  6. Jul 25, 2012 #5
    what liquid should i use then?what liquid has lowest vapor pressure?
     
  7. Jul 25, 2012 #6

    Drakkith

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    Staff: Mentor

    If you want to make a vacuum you can shoot electrons through you will probably need a decent vacuum pump.
     
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