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Question about manometers

  1. Sep 4, 2010 #1

    The teacher said that one way to measure the pressure of a gas enclosed in a room is to attach a manometer to it, like in that picture:
    [PLAIN]http://img842.imageshack.us/img842/3994/manometer.jpg [Broken]

    By doing so, aren't we changing the volume the gas has access to, and thus changing the pressure of the gas?

    Thank you very much
    Last edited by a moderator: May 4, 2017
  2. jcsd
  3. Sep 4, 2010 #2
    Yes, there will be volume increase so decrease in pressure in the system. But there is no difference how big the diameter of the tube will be so more precise measurement you will have if the diameter of the tube is small so the increase of volume is small in respect of the volume of the system so you dont take it in to account.
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