Lakhmir Singh Physics Class 10 Solutions Page No:148
Question 1: What substance is obtained as a residue when wood is burned in a limited supply of air ?
Solution : Charcoal.
Question 2: Name one source of energy which is not derived from solar energy directly or indirectly.
Solution : Geothermal energy.
Question 3: What name is given to the heat energy obtained from hot rocks inside the earth ?
Solution : Geothermal energy.
Question 4: Name the agent which decomposes animal dung into biogas.
Solution : Anaerobic bacteria.
Question 5: Which component of biogas is used as a fuel ?
Solution : Methane.
Question 6: Name the constitutents of biogas.
Solution : Bio gas consists of methane, carbon dioxide, hydrogen and hydrogen sulphide.
Question 7: Which of the following is needed for the formation of biogas from cow-dung and which not ?
Solution : Needed:- water.
Not needed:- oxygen.
Question 8: Name the clean fuel which can be obtained from cow-dung.
Solution : Biogas.
Question 9: Apart from cattle dung, what other substances can be added to a biogas plant ?
Solution : Apart from cattle dung, human excreta, agriculture wastes, vegetable wastes, poultry droppings, paper scrap etc. can also be added to a biogas plant.
Question 10: Name any three forms of energy which could be harnessed from the sea.
Solution : Three forms of energy which could be harnessed from the sea are:
(i) Tidal energy
(ii) Wave energy
(iii) Ocean thermal energy.
Question 11: Write two forms in which solar energy manifests itself in sea.
Solution : (i) Sea-waves energy.
(ii) Ocean thermal energy.
Question 12: Write the full form of OTE.
Solution : OTE stands for Ocean Thermal Energy.
Question 13: What is the function of anaerobic micro-organisms such as anaerobic bacteria in a biogas plant ?
Solution : Anaerobic bacteria help in the degradation of cow-dung in the presence of water but in the absence of oxygen.
Question 14: State whether the following statement is true or false :
Tidal energy is one of the forms in which solar energy manifests itself in oceans.
Solution : False
Question 15: 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.
Solution : (a) solar. (b) twice.
Question 16: (a) What is biomass ? Give three examples of biomass.
(b) Name the biomass which is still widely used as a source of heat energy in many households of our country.
Solution : (a) The dead parts of plants and trees, and the waste material of animals are called biomass. It is the organic matter which is used as a fuel to produce energy. E.g., wood, agricultural wastes and cow dung.
Question 17: What are the two ways in which cow-dung can be used as a fuel ? Which of them is better and why ?
Solution : Two ways in which cow-dung can be used as a fuel are:
1. In the form of cow-dung cakes, which can be used directly as a fuel.
2. By preparing biogas from cow-dung.
Biogas is better than cow-dung cakes because it gives a cleaner than cow-dung cakes and after extracting biogas, the spent cow-dung can be used as a manure.