Syllabus

📘 Barometer – Short and Long Answer Type Questions

1. What is atmospheric pressure?

Atmospheric pressure is the pressure exerted by the weight of the air in the Earth's atmosphere on objects on Earth.

2. Why don’t we feel the atmospheric pressure acting on us?

We don't feel it because the pressure inside our body balances the atmospheric pressure from outside.

3. Describe an experiment to show that air exerts pressure.

Take an empty can and heat it with some water inside. When steam comes out, close the lid tightly and cool it. The can collapses due to air pressure.

4(i). Why does a balloon collapse when air is removed?

When air is removed from the balloon, the external atmospheric pressure crushes it as no air is left inside to balance it.

5. Why does liquid rise in a syringe when its piston is pulled up?

Pulling the piston reduces pressure inside the syringe, so the atmospheric pressure on the liquid surface pushes it up into the syringe.

6. How is water drawn up from a well using a pump?

The pump reduces pressure inside the pipe, so atmospheric pressure pushes water up from the well into the pipe.

7. Why is the mercury column height in a barometer a measure of atmospheric pressure?

Atmospheric pressure supports the mercury column. Greater pressure supports a higher column and vice versa.

8. Why is barometric height used to measure atmospheric pressure?

Because atmospheric pressure is directly proportional to the height of mercury in the barometer.

9. Why is mercury used as a barometric liquid?

Because mercury is dense, requires a shorter column, and does not stick to the glass or evaporate easily.

10. Give two reasons why water is not a suitable barometric liquid.

Water has low density and high evaporation. It would need a very tall tube (over 10 meters).

11. What is the name of the vacuum above mercury in a barometer?

Torricellian vacuum.

12. What is the average height of the mercury column at sea level?

76 cm of mercury (Hg).

13. How does atmospheric pressure change with altitude?

Atmospheric pressure decreases with altitude because the air becomes thinner as we go higher.

14. Why does a fountain pen leak at high altitude?

At high altitudes, atmospheric pressure decreases, so the pressure inside the pen becomes greater and pushes the ink out.

15. Why does our nose bleed on mountains?

The lower air pressure outside causes internal pressure in blood vessels to burst, leading to nosebleeds.

16. What are two advantages of an aneroid barometer?

1) Portable and compact
2) Can record pressure continuously with a pointer and scale.

17. Mention two demerits of a simple barometer.

1) Bulky and breakable
2) Mercury is poisonous and evaporates slowly.