Three factors responsible for creation of wind are
1. Difference in temperature in the polar (cool) and equatorial regions.
2. Rotation of the earth.
3. Local conditions.
Principle of working windmill:
The blades of a windmill are designed in such a way that when wind blows over them, a pressure difference is created over the different regions. This pressure difference rotates the blades.
To produce electricity, the rotatory motion of blades is utilized to rotate the armature of an electric generator. In a water lifting machine, the rotatory motion of the blades is made to do mechanical work.
Advantages of using wind energy:
(i) It does not cause pollution in the environment.
(ii) The cost of using fuel (i.e., air) is nil.