Name the reaction responsible for large energy production in the sun.

$(a)$ 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.

$(a)$ Why is the solar cooker box covered with a plane glass plate?
$(b)$ Why is energy of water flowing in a river considered to be an indirect form of solar energy?
$(c)$ How is the fission of ${}^{235}U$ nucleus brought about?

Why is charcoal considered to be a better fuel than wood? What are the disadvantages of converting wood into charcoal?

State any two impacts on the environment caused due to the increase in energy demand. Suggest any two steps to reduce energy consumption.

Mention any two differences between the two common designs of solar cooker.