CBSE Class 10 Answered

We saw earlier that we cannot depend on the fossil fuels for much longer. Such sources that will get depleted some day are said to be exhaustible sources or non-renewable sources of energy. On the other hand, if we manage bio-mass by replacing the trees we cut down for fire-wood, we can be assured of a constant supply of energy at a particular rate. Such energy sources that can be regenerated are called renewable sources of energy. 1. What kind of mirror – concave, convex or plain – would be best suited for use in a solar cooker? Why? 2. What are the limitations of the energy that can be obtained from the oceans? 3. What is geothermal energy? 4. What are the advantages of nuclear energy? 254 Science QUESTIONS QUESTIONS ? 1. Name two energy sources that you would consider to be renewable. Give reasons for your choices. 2. Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices. What you have learnt „ Our energy requirements increase with our standard of living. „ In order to fulfil our energy requirements, we try to improve the efficiency of energy usage and also try and exploit new sources of energy. „ We also need to look for new sources of energy because the conventional sources of energy like fossil fuels are in danger of getting exhausted soon. „ The energy source we select would depend on factors like the ease and cost of extracting energy from the source, the efficiency of the technology available for using that source of energy and the environmental impact of using that source. „ Many of the sources ultimately derive their energy from the Sun. EXERCISES 1. A solar water heater cannot be used to get hot water on (a) a sunny day. (b) a cloudy day. (c) a hot day. (d) a windy day. Activity 14.9 „ Debate the following two issues in class. (a) The estimated coal reserves are said to be enough to last us for another two hundred years. Do you think we need to worry about coal getting depleted in this case? Why or why not? (b) It is estimated that the Sun will last for another five billion years. Do we have to worry about solar energy getting exhausted? Why or why not? „ On the basis of the debate, decide which energy sources can be considered (i) exhaustible, (ii) inexhaustible, (iii) renewable and (iv) non-renewable. Give your reasons for each choice. Renewable energy is available in our natural environment, in the form of some continuing or repetitive currents of energy, or is stored in such large underground reservoirs that the rate of depletion of the reservoir because of extraction of usable energy is practically negligible.