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Homework Help: Gas Thermometer

  1. Sep 1, 2013 #1
    The Question is in the paint document.

    My question to this problem is at the bottom of thread 1

    T = T3/P3P. Where
    T3 is the temperature (K) of water at triple point
    I am not 100% sure what P and P3 stand for (can someone tell me)
    I believe P is the net pressure (Pressure supplied by the bulb minus the pressure opposing the pressure supplied by the bulb)
    and P3 is the pressure at triple point.

    All Temp are in Kelvin (K)

    TL = Temp of left bulb
    PL = Pressure of left bulb
    TR = Temp of right bulb
    PR = Pressure of right bulb

    First Step:

    Let TL = T3 and TR = Boiling Point of Water = (BP)

    TL - TR = T3 - (BP) =
    T3/P3(PL - PR)

    Because (TL - TR)<0 Then (PL - PR) = -120torr.

    Solving for P3:

    P3 =T3(PL - PR)/(T3 - (BP))

    Second Step:
    Let TL = T3 and TR = Unknown Temp. (T)

    TL - TR = T3 - T = T3/P3(PL - PR)

    Solving for T:
    T = T3 - T3/P3(PL - PR)

    Because I dont know If T>T3 or T<T3 I do not know whether (PL - PR) = +90torr or -90torr.

    How am I suppose to know?

    Attached Files:

    • Temp.jpg
      File size:
      19.1 KB
    Last edited: Sep 1, 2013
  2. jcsd
  3. Sep 1, 2013 #2


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    Staff Emeritus
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    The Paint document didn't make it thru the posting process. Please repost the attachment.
  4. Sep 2, 2013 #3
    I figure it out:

    Let TL = Temp left bulb
    PL = Pressure Left bulb
    TR = Temp right bulb
    PR = Pressure Right bulb

    I will keep TR constant at triple point and vary TL:

    First Phase: The pressure difference was 120torr when one bulb was at triple point and the other was at boiling point.

    If PL - PR = 120then TL>TR

    Second Phase: The pressure difference was 90torr when one bbulb was at triple point and the other was at an unknown temperature (T)

    If PL - PR = 90 then T>TR
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