Physics
Why is the barometric height used as a unit to express the atmospheric pressure ?
Fluids Pressure
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Answer
If the atmospheric pressure increases, the pressure at point C increases and mercury from trough flows into the tube thereby increasing the vertical height of mercury column in the tube so as to equalise pressures at points A and C.
On the other hand, when the atmospheric pressure decreases, the vertical height of the mercury column decreases to balance it.
Thus, the vertical height of the mercury column from the mercury surface in the trough to the level in the tube, is a measure of the atmospheric pressure.
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