Barometer

A barometer is an instrument used to measure the air pressure as it varies with distance either above or below sea level. Italian scientist Evangelista Torricelli invented the barometer in the year 1643. He studied the characteristics of mercury when placed in a vacuum and used that theory to develop the first barometer.

Table of Contents

How does a Barometer work?

The working of a barometer depends on balancing mercury weight in the glass tube with respect to the atmospheric pressure. If the weight of the mercury is less than atmospheric pressure, the mercury level will increase. And if the weight of the mercury is more than the atmospheric pressure, the mercury level will decrease. The rising and falling of the mercury are measured using the inch scale marked on the glass tube.

Types of Barometer

A barometer is divided into two types as follows: 

  • Mercury Barometer
  • Aneroid Barometer

Mercury Barometer

This is the most commonly used barometer. Torricelli invented this in the year 1643. It consists of a glass column with mercury and inches markings on it. The top end of the tube is closed and the bottom end is rested in a cup containing mercury known as a cistern. To increase the accuracy, these barometers are corrected for ambient temperature and the local value of gravity. The reason why mercury is used is because of its density.

Aneroid Barometer

This barometer is made without fluid. It consists of an aneroid capsule, a thin and flexible metal box made from an alloy of beryllium and copper. For better expansion and contraction of levers and springs of the box, which is due to a change in atmospheric pressure outside the box, the box is tightly sealed.

How to Make a Barometer?

Science Exhibition Models

Predict the type of weather near you by watching a barometer. As discussed, a barometer is a type of instrument that measures air pressure. Low pressure usually means rainy weather, while high pressure means mild cool weather. Well, you don’t need to be a weather expert to understand the weather patterns. Build Your Barometer by gathering the things listed below and following the steps mentioned diligently.

Things you will need

  • Permanent Marker
  • Solid paper- Card like
  • Straw
  • Transparent Tape
  • Rubber Band
  • Jar
  • Scissors
  • Balloon

Procedure

  • Take the balloon and cut its top off.
  • Take and rubber band and use it to fix the cut balloon over the jar by stretching it out.
  • The straw will be fixed over the balloon (use the tape) and in such a manner that one-third of it hangs over the edge.
  • Use a scale and draw three lines over the card at an equal space of half a centimetre. These lines will be labelled as low, moderate, and high.
  • The card should be taped to the backside of the jar, making the straw point towards moderate.
  • Place this apparatus somewhere indoors on a flat surface.

In a low-pressure situation, the balloon will swell up, and the straw will start pointing downwards. This happens due to the air pressure difference as the air inside has a higher pressure than outside, thus expanding, and thus it expands the balloon out.

Similarly, the external air will push the balloon inside in a high-pressure environment, and the straw will point upwards. This happens as the air in the balloon has low pressure. In general, low pressure results in bad weather, whereas high pressure results in good weather. You can create a full weather report by combining several factors such as wind direction and speed, and rainfall.

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Frequently Asked Questions – FAQs

What is a Barometer?

A barometer is an instrument used to measure the air pressure as it varies with distance either above or below sea level.

Who invented the barometer?

Italian scientist Evangelista Torricelli invented the instrument in the year 1643.

How does a barometer work?

The working of a barometer depends on balancing mercury weight in the glass tube with respect to the atmospheric pressure.

How many types of barometers are there?

There are two types of barometers namely: mercury barometer and aneroid barometer.

Which is the commonly used barometer?

Mercury barometers are commonly used.

Watch the video to understand how does the air pressure help us in predicting the weather!

Stay tuned with BYJU’S to learn more about other Physics related concepts.

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