How does a barometer work?

Weather Instrument

A barometer tells us what the weather may be like by measuring changes in air pressure.   A barometer is an instrument that measure the pressure of air.

The ocean of air above us pushes down on the earth with a great deal of force.   Just as a scale measures the pressure of your weight, so the barometer tells the weight of the air above it.

There are different kinds of barometers.   Barometers called “aneroid barometers” record changes in air pressure by using an air light box from which most of the air has been removed.

Changes in air pressure causes the box to expand or contract.  These changes controls a pointer on a dial.

When we read a mercury barometer, we read the height of mercury in a glass tube.  Changes in air pressure causes the mercury to rise or fall.  Barometer are very useful to the weatherman.

When the mercury falls rapidly, he knows a storm is quite likely to follow.  A “rising barometer” often foretells better weather – Dick Rogers

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1 Comment

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