CLASS X SCIENCE STUDY MATERIAL
- 1. SOURCES OF ENERGY Q1. (a) How does constructionof dam across the river get linked with production of greenhouse gases? (b) How does biogas plant help to reduce the problem of pollution? Ans. (a) A vast variety of plants get submerged in water, rot under anaerobic conditions and produce large amount of green house gases such as methane. (b) Bio gas plant helps to reduce the problem of pollution in the following ways- i) It provides better sanitation due to safe disposal of bio-waste and sewage material. (ii)Bio gas obtained from this plant produces less smoke on burning. (iii) The residue left can be used as a manure which can be used as an alternative of fertilisers. Thus, it prevents soil and water from degradation. Q2.(a) What is geothermal energy? (b) What are the advantages of wind energy? Ans.(a) The heat energy obtained from the molten rocks formed in the deeper hot regions inside the earth are called geothermal energy. (b) Advantages of wind energy are- (i) It is an inexhaustible source of energy. (ii) It does not cause any environmental pollution. (iii) It is available free of cost. Q3. List any four reasons why we need to look for alternate sources of energy? Ans. We are looking for alternate sources of energy because- (i)The fossil fuel reserves in the earth are limited which may get exhausted soon, if continued to be used at the current rate. (ii)If alternate sources of energy are used, the fossil fuels would last for much longer time. (iii)Alternate sources of energy do not cause pollution, they are eco friendly. Q4.(a) State the principle of working of ocean thermal energy conversion plant. (b) Suggest the steps to minimise the pollution caused by various sources of energy.
- 2. Ans. (a) Principle of working of OTEC: The water at the surface of the ocean is warmer than the water at deeper depths. The temperature difference can be used by OTEC system to generate electricity. (b) Following steps can be taken to minimise pollution: i) Use of smokeless appliances. ii) Use of refined technology to increase the efficiency of combustion process and to reduce escape of harmful gases into the atmosphere. iii) Judicious use of energy. Q5. What are the limitations of extracting energy from (i)The wind (ii) Waves (iii) Tides Ans.(i) a) It is not available all the time. b) It requires a very large area of land. c) It is not possible to have a windmill everywhere as to run it, the minimum wind speed of 15km/h is required. (ii) a) Wave energy can be harnessed only where waves are very strong. b) Set up is very costly. (iii) a) Very few sea coasts in the world have suitable sites for the purpose of harnessing tidal energy. b) The rise and fall of tides happen only twice in a day and is not sufficient to generate electricity continuously.