question_answer

  (a) Name the places of our country where fields of natural gas are found. Why is it called a clean fuel? Give two reasons. (b) Why is there so much emphasis on changing over from petrol/diesel driven automobiles to CNG driven vehicles. Or (a) (i) What conversion of energy takes place in wind mill? (ii) What is the minimum wind velocity required to obtain useful energy with a windmill? (iii) Give one limitation of windmill. (b) Hydro energy is an indirect source of solar energy. Justify.

Answer:

  (a) The places where fields of natural gas are found are Tripura, Jaisalmer, Off-shore area of Bombay, Krishna-Godavari Delta.                                                                                                                                                                 (1)                                                                       Natural gas is a clean fuel because of the following reasons (i) It does not produce harmful gases on burning. (ii) It burns without smoke and does not leave any residue after burning.                                             (1 x 2) (b) There is so much emphasis on changing over from petrol /diesel driven automobiles to CNG driven vehicles, because of the following reasons (i) CNG it does not produce smoke. (ii) CNG it does not leave unburnt hydrocarbons, lead particulates, etc which pollute the environment. (2) Or (a) (i) In windmill kinetic energy of wind is converted into electrical energy.                                                         (1) (ii) 15 km/h is the minimum wind velocity required to obtain energy.                                                                      (1) (iii) Wind does not blow at sufficiently high speed all the time.                                                                                   (1) (b) Solar energy is manifested in many forms on earth, one of which is hydro energy. During water cycle, water flowing in rivers and other water bodies evaporates by the heat of sun, condenses, moves back in upper atmospheric layers and gets replenished back. Thus, energy of flowing water is attributed to the sun.                                                                                                                                                                                                    (2)