Advertisements
Advertisements
Question
Draw a simple diagram of a Fortin's barometer and state how it is used to measure the atmospheric pressure.
Advertisements
Solution
Fortin barometer is used to measure atmospheric pressure.
Before reading the Fortin barometer, the free surface of the mercury in the reservoir is made to touch the tip of the ivory pointer by raising or lowering the level with the help of the screw S2. The vernier scale is then adjusted with the screw S1 till its lower edge touches the upper meniscus of mercury in the tube. While making this adjustment the eye is kept in level with the mercury meniscus. For this adjustment, the vernier is moved till the wall of the glass plate just ceases to be visible through the slits. The vernier can read to 1/ 20 mm or 1/ 500 inch. The reading of the barometer then gives the true atmospheric pressure. A thermometer is usually provided with the barometer which is also read and correction is made for the expansion of scale with a rise in temperature and also for the change in density of mercury with temperature. The scale graduations are correct only for the temperature at which the graduations are made.
APPEARS IN
RELATED QUESTIONS
Write the numerical value of the atmospheric pressure on the earth surface in pascal.
We do not feel uneasy even under the enormous atmospheric pressure. Give a reason.
Describe a simple experiment to illustrate that air exerts pressure.
Explain the following :
A balloon collapses when air is removed from it.
State two advantages of an aneroid barometer over a simple barometer.
Why are the months of January and July used to describe the world distribution of pressure?
The standard air pressure at sea level is ______.
High pressure is called ______.
Figure shows a child blowing air with a straw near the opening of another straw which has its other end in a soft drink bottle. It was observed that the level of the soft drink in the straw rises up as soon as air is blown over its open end. Which one of the following best explains the reason for rise in level of the drink?
Briefly explain the concept of variation of atmospheric pressure.
