Rotating Capillary Tube Experiment


Capillary tube with mercury, ruler, plumb line, metre ruler and clamp stand.


1. Measure the length of the air column,(in mm) as a function offrom= 0 to= 180 .can be found by measuring (with the aid of a metre rule and the plumbline)and as defined in the diagram above (Do not use a protractor).

2. Measure the length of the mercury index, a (in mm) .

3. Draw a graph of(in)againstand hence use it to find the atmospheric

pressure(in mm of mercury). (See below for theory).

4. Compare the value of atmospheric pressure found by using this method with the value measured using the Fortin barometer in the corridor.

Theory : From Boyle's Lawwithmm of mercury

and[andare constants].

Boyle's law become[is another constant]

thereforeand so


Compare this with the equation of a straight line

Measure (or calculate) the gradient,and the- intercept,

And so findwhere

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