1. Unit 3 Nature’s Energy 1

2. 3. Wind Energy

3. The sun heats air by convection
The convection currents that move through heated water also
Move through heated air

4. The moving air is called wind
You cannot see wind,
only the results of the wind energy

5. Vocabulary
Wind energy
Energy of moving air

6. Wind is caused by heat from the sun
The sun warms the surface of the
Earth

7. Some parts of Earth’s surface, such as roads and beaches,
absorb or take in more heat than others

8. The air over these areas becomes warmer than the air around them
This warm air rises, and the cool air around it moves in to take its place

9. This convection current happens anywhere that air becomes heated
Sometimes the air moves slowly

10. You cannot feel the wind when it moves slowly
Sometimes it moves fast.

11. Any matter that is moving is using
Wind is a source of
mechanical energy
Any matter that is moving is using
mechanical energy

12. The wind can move things.
A very strong wind can push over
trees and buildings

13. One of the ways people first used wind energy was to power sailboats.
As the wind pushes against the sails, it moves the boat across the water

14. are another way people use
Windmills
are another way people use
wind energy

15. A windmill has flat blades on a wheel
Wind pushes the blades and
makes the wheel turn.

16. The energy of the turning wheel can be used to pump water from a well
It can also be used to make electricity

17. People have been using windmills for more than a thousand years