1. Air Pressure and Wind

• Wind: Moving air is called wind. Air moves from a region of high pressure to a region of low pressure.
• Air Pressure: Air exerts pressure in all directions.
  Example: Leaves fly, banners flutter, and bicycle tubes keep shape due to air pressure.
• High Speed Winds: Increased wind speed is accompanied by reduced air pressure.
  Activity: Blowing over a strip of paper makes it lift up because pressure above it decreases.

2. Air Expands on Heating

• Expansion: When air is heated, it expands and occupies more space. It becomes lighter and rises up.
• Contraction: Cold air is heavier and sinks down.
• Natural Phenomenon: Smoke always rises because it is hot.

3. Wind Currents

Wind currents are generated due to uneven heating on the Earth:

• Equator vs Poles: Regions near the equator get maximum heat. Warm air rises, and cooler air from 0-30° latitude moves in.
• Land vs Water: In summer, land heats up faster than oceans. Wind blows from Ocean to Land (Monsoon winds carrying water). In winter, wind blows from Land to Ocean.

4. Thunderstorms and Cyclones

• Thunderstorms: Develop in hot, humid tropical areas like India. Rising temperatures produce strong upward winds carrying water droplets, which freeze and fall, creating lightning and sound.
• Cyclones: A huge revolving storm caused by low pressure.
  Formation: Water vapor condenses -> releases heat -> warms air -> air rises -> low pressure -> more air rushes in -> cycle repeats.
  Structure: The calm center is called the Eye.
• Tornadoes: A dark funnel-shaped cloud reaching from the sky to the ground.

5. Safety Measures

• Cyclone Alert: Issued 48 hours in advance. Cyclone Warning: 24 hours in advance.
• Action: Do not ignore warnings. Shift to shelters. Do not touch wet switches. Store drinking water.