What substance is obtained as a residue when wood is burned in a limited supply of air?

Name one source of energy which is not derived from solar energy directly or indirectly.

What name is given to the heat energy obtained from hot rocks inside the earth?

Name the agent which decomposes animal dung into biogas.

Which component of biogas is used as a fuel?

Name the constituents of biogas.

Which of the following is needed for the formation of biogas from cow-dung and which not?

Water, Oxygen

Name the clean fuel which can be obtained from cow-dung.

Apart from cattle dung, what other substances can be added to a biogas plant?

Name any three forms of energy which could be harnessed from the sea.

Write two forms in which solar energy manifests itself in sea.

Write the full form of OTE.

What is the function of anaerobic micro-organisms such as anaerobic bacteria in a biogas plant?

State whether the following statement is true or false:

Tidal energy is one of the forms in which solar energy manifests itself in oceans.

Fill in the following blanks with suitable words:

(a) Biomass is another form in which .......... energy manifests itself.

(b) Tidal waves build up and recede .............. a day.