question_answer 23)

Name two energy sources that you consider to be renewable. Give reasons for your choices.  

Answer:

(i) Water energy (hydro-energy); (ii) biomass energy. Water on Earth can be used again and again to generate hydro-energy as obvious from water cycle in nature. Solar energy also appears in the form of energy of water flowing in the rivers. This is obvious from the water cycle in nature which is as follows. (a) Solar energy changes into potential energy of water vapour rising in the atmosphere during evaporation of water from rivers, seas, oceans and other water masses. The water vapour form clouds and also cover mountains with snow. (b) When the clouds bring rain and the snow on the mountains melts their potential energy changes into the kinetic energy of water flowing in the river and streams. Biomass can be managed by replacing the trees that have been cut down for fire-wood. By doing so, we can get a constant supply of energy at a particular rate.