Lakhmir Singh Physics Class 10 Solutions Page No:161
Question 1: Which of the two is a cleaner fuel : hydrogen or CNG ? Why ?
Solution : Hydrogen is a cleaner fuel because burning of hydrogen produces only water. which is harmless; but burning of CNG produces CO2 and water. CO2 produces greenhouse effect.
Question 2: Which of the two is more energy efficient: filament type electric bulb or CFL ? Why ?
Solution : CFL is more energy efficient because it wastes much less energy as heat than filament type electric bulb.
Question 3: How long are the energy resources of the earth like coal, petroleum and natural gas expected to last ?
Solution : Coal – 200 years
Petroleum – 40 years
Natural Gas – 60 years
Question 4: Name two devices which can be utilised for the cooking of food so as to save fuel .
Solution : Solar cooker; pressure cooker
Question 5: What are the various factors which we should keep in mind while choosing a source of energy ?
Solution : Various factors to be kept in mind while choosing a source of energy are:
1. the ease of extracting energy from that source
2. the cost of extracting energy from that source
3. the efficiency of technology available for extracting energy from that source
4. the damage to environment caused by using that source
Question 6: Can any source of energy be pollution free ? Explain your answer with an example.
Solution : No. No source of energy is pollution free.
For e.g., the use of wind generators is pollution-free but the processes involved in making it must have damaged the
Question 7: What are the environmental consequences of the increasing demand for energy ?
Solution : The environmental consequences of the increasing the demand for energy are:
(i) The combustion of fossil fuels is producing acid rain and damaging plants, soil and aquatic life.
(ii) The combustion of fossil fuels is increasing the green house effect.
(iii) Nuclear power plants are increasing radioactivity in the environment.
(iv) Construction of hydro-power plants is disturbing the ecological balance.
Question 8: What steps would you suggest to reduce energy consumption ?
Solution : Steps for reducing the energy consumption:-
(i) Switch off all the lights, fans, TV and other appliances when not needed.
(ii) Use of biogas as cooking fuel should be encouraged.
(iii) Bicycles should be used for short distances to save precious fuels like petrol.
(iv) Solar cookers should be used to cook food.