Give one example each for renewable and non-renewable sources of energy.

Biomass has been used as fuel since ancient times. How has it been modified to function as a more efficient fuel in the recent past?

The chief constituent of biogas is methane. List any two other constituents of biogas.

What is biogas? How can biogas be obtained? Why is the use of biogas obtained from cow dung advised in preference to burning cow dung cakes?

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?

Compare and contrast fossil fuels and the Sun as direct sources of energy.