Why do we need Air?

Air is all around us and is essential for survival. We breathe in oxygen from the air to stay alive. Without air, neither humans nor animals can survive, and plants also depend on carbon dioxide from air for photosynthesis.

Composition of Air

Air is a mixture of gases. It mainly contains Nitrogen (78%), Oxygen (21%), and about 1% other gases such as carbon dioxide, argon, and water vapour.

• Nitrogen – provides balance, prevents oxygen from burning things too quickly.
• Oxygen – supports breathing and burning.
• Carbon dioxide – required by plants to make food.

Other gases – include argon, water vapor, and trace gases.

Activity 1: Breathing Exercise

Description: Students take deep breaths, hold their breath, and then release.

• This shows that oxygen in air is necessary for survival.
  
• Holding breath makes us uncomfortable because our body cannot function without oxygen for long.

Activity 2: Making a Firki (Pinwheel)

Description: Students make a small paper pinwheel and run with it or blow air on it.

• The firki rotates when air moves, showing that moving air (wind) has force.
  

This is the same principle used in windmills.

Wind as a Source of Energy

Just like the firki, wind turns the blades of a windmill. This motion can be used to:

• Pump water from wells.
• Run flour mills.
• Generate electricity in wind farms.

Working of a Windmill / Wind Turbine

1. Wind Blows → Blades Rotate
   • The wind pushes against the turbine blades, causing them to spin.
   • The blades are shaped like airplane wings to capture maximum energy.
2. Rotor Spins → Shaft Turns
   • The spinning blades are connected to a rotor, which turns a main shaft inside the turbine.
3. Gearbox Increases Speed
   • The shaft is connected to a gearbox that increases the rotation speed.
   • This is important because the generator needs high-speed rotation to produce electricity efficiently.
4. Generator Produces Electricity
   • The high-speed shaft turns a generator, which converts mechanical energy into electrical energy using electromagnetic induction.
5. Electricity is Transmitted
   • The electricity flows to a transformer inside or near the turbine.
   • The transformer increases the voltage so the power can travel long distances through power lines.
6. Distribution to Homes
   • The electricity is sent to the power grid.
   • From the grid, it is distributed to houses, schools, factories, etc., where it is converted back to the lower usable voltage.

Example: Muppandal Wind Farm in Tamil Nadu is one of India’s largest wind farms.

Applications of Air in Daily Life

• Breathing – Oxygen in air keeps humans and animals alive.
• Plants’ food – Carbon dioxide helps plants prepare food.
• Burning – Fire needs oxygen to keep burning.
• Wind energy – Windmills produce clean electricity.
• Movements in nature – Wind helps in pollination, spreading seeds, and flying kites.