Name any two renewable sources of energy.

Ram visited Manikaran Sahib in Himachal Pradesh where he saw an experimental geothermal plant. When he saw a hot spring,he wanted to know more about it. His father explained to him about geothermal energy and hot springs. Now answer the following questions:
$(a)$ What did Ram's father explain to him about hot springs?
$(b)$ Why is geothermal energy not generated on a large scale?
$(c)$ What is the main advantage of using geothermal energy?

Name the fuel that provides most of the energy needs of the world.

The energy liberated by burning $1 \, g$ of wood is approximately: (in $, kJ/g$)

What is biomass? Explain the principle and working of a biogas plant using a labelled schematic diagram.

Give two uses of coke.