State whether the following statement is true or false:
Solar energy has the greatest potential of all the renewable sources of energy.

Mention any two advantages and two disadvantages of producing hydroelectricity by building dams on rivers.

$(a)$ Describe the structure of a windmill.
$(b)$ Give one example to illustrate that energy from a windmill was used in the past to do mechanical work.

What are the limitations in obtaining energy from wind?

Solar cooker takes more time as compared to the $LPG$ to boil potato or rice,yet Kunal uses solar cooker for such type of cooking:
$(a)$ Why does Kunal use solar cooker instead of $LPG$? Give reason for your answer.
$(b)$ Name the phenomenon which is responsible for obtaining high temperature in solar cooker?
$(c)$ What is the motivation behind using solar cooker?

Name any two materials that are used to make solar cells.