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Manometers calculation P=pgh?

  1. Sep 7, 2008 #1
    Hi All,

    When reading Manometers, does the internal diameter of the manometer have a bearing on the readings & the calculation P=pgh??
    There is no inclusion of the ID of the manometer tubing.

    If we apply pressure to a manometer tube say of 2mm inside diameter the height will be X but now we use a 20mm inside diameter tube, the volume is more of course so do we get the same h value with the larger diameter. The mass of the fluid is more so for the same pressure it would seem the h value will be different?

  2. jcsd
  3. Sep 7, 2008 #2


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    Staff: Mentor

    Re: Manometers

    You'll notice that pressure is in units of area, which means that it is independent of the area of the object it is acting on. You may be confusing pressure with force. Force is pressure times area.
  4. Sep 8, 2008 #3
    Re: Manometers

    Thanks Russ,
    Good explanation!
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