Question

Which of the following scientists invented mercury barometer?
(A)Blaise Pascal (B) Evangelista Torricelli (C) Robert Brown (D) Amedeo Avagadro

Answer 1

Hint: Barometer is a device which is used to measure air pressure. Think in terms of different scientists and their contributions to reach the answer.

Complete step by step answer:
In earlier days , it was thought that a true vacuum ( space devoid of matter) could not exist because the surrounding matter would fill up the space. Most scientists thought that air does not have any weight and hence it cannot exist under any pressure. However, Evangelista Torricelli put a full stop to all these misconceptions with his invention. He worked with tubes filled with mercury ( mercury is denser than water).

How a barometer was constructed:
1) Take a glass tube of some measured length.
2) The glass tube should be open at one end and sealed at the opposite end.
3) Fill the tube with mercury.
4) Invert the glass tube upside down over a trough filled with mercury ( same liquid as that in the tube).
5) Make sure the air does not enter by any means.
The liquid inside the tube shows some movement i.e. it either goes up or down . Now ,if there is no sort of pressure present there. What made it happen? This proves that the air has weight and that it exerts some pressure. The pressure outside the glass tube causes the mercury to move up and down to balance the pressure inside and outside the tube.
If the pressure outside the glass tube is more, it causes the mercury level to rise up inside the tube . And if the pressure inside the glass tube is less ,it causes the mercury level to decrease. As mercury level rises up and down inside the tube, a vacuum is created.
Hence, the correct option is (B).

Note: The invention of the mercury barometer has been playing a very vital role in the forecasting of weather, determining the altitude of a place , calibration and so on.