"AKC SCIENCE CLASSES"
CLASS 10 TH (CBSE AND MP BOARD)
CHAPTER 14
SOURCES OF ENERGY
INTEXT QUESTIONS AND ANSWERS
NCERT INTEXT QUESTIONS (PAGE NO. 243)
Q.01:- What is a good source of energy?
Ans:- A good source of energy would depends on the requirement for which energy is needed. For example, we use one source say gas for cooking food and another source say electricity for heating a room. In general a good source of energy would be one
- which would do a large amount of work per unit mass/volume.
- Which would be easily accessible.
- which can be easily stored and transported.
- which is also reasonably economical.
Ans:- Following should be the characteristics of a good fuel :-
- It should be fairly cheap.
- It should be easily available.
- Its ignition temperature should be reasonably above normal temperature.
- It should be conveniently handled and transported.
- It should not produce, during burning, any poisonous materials or irritating fumes etc.
- Its combustion rate should be steady and controllable.
- It should not leave any residue or ash after burning.
- It should burn in a way that can be controlled.
Ans:- We would prefer to use cooking gas like LPG or PNG. It fulfils many of the criteria of a good fuel, most importantly like its ignition temperature, good calorific value and non-pollution characteristics.
NCERT INTEXT QUESTIONS (PAGE NO. 248)
Q.01:- What are the disadvantages of fossil fuels?
Ans:- Burning of fossil fuels produces oxides of carbon, nitrogen and sulphur. These lead to acid rain which affects our water and soil resources. These gases also cause many health hazards and are extremely harmful to asthmatic patients. Carbon dioxide produced cause greenhouse effect which is responsible for global warming.
Q.02:- Why are we looking at alternate sources of energy?
Ans:- The most important, convenient and largely developed conventional source of energy are fossil fuels like petroleum and coal. Besides causing pollution problems, these sources are not renewable sources and with modern development and large scale usage, their stocks are depleting. We would thus in future have serious energy crisis. Therefore, it is urgently required to look for alternate source of energy.
Q.03:- How has the traditional use of wind and water energy been modified for our convenience?
Ans:- Water energy :- To use water energy for producing electricity, a large number of high rise dams are constructed on the suitable river spots to obstruct the flow of water and collect water in large reservoirs. The kinetic energy of the flowing water is converted into potential energy. Then the water from the high level in the dam is carried through pipes to the turbine at the bottom of the dam. Thus the potential energy of falling water is converted into electrical energy.
Wind energy :- Windmill farms are constructed at places where wind flows for greater part of the year at a speed greater than 15 km/h. The kinetic energy of the wind is converted into rotatory motion of the windmill. Then the rotatory motion of the windmill is used to turn the turbine of electric generator.
NCERT INTEXT QUESTIONS (PAGE NO. 253)
Q.01:- What kind of mirror concave, convex of plane would be suited for use in solar cooker? Why?
Ans:- A plane mirror is used because it reflects all the light falling on it to the desired place.
Q.02:- What are the limitations of the energy that can be obtained from the oceans?
Ans:- Energy from the sun can be tapped in three different ways :-
(1). Tidal energy :- The tidal energy can be harnessed by constructing dams across some narrow openings in the sea. Such sites are limited and the electricity generated is not high enough to be commercially viable.
(2). Wave energy :- The movement of ocean waves is associated with kinetic energy. Such sites in the world are limited where the waves strike the shorelines with sufficient power.
(3). Ocean thermal energy :- To convert ocean thermal energy into electricity, it is necessary that a difference of more 20℃ between the surface waters and water at depths of 1000 metres is required. This is again involved high cost.
Q.03:- What is geothermal energy?
Ans:- The interior or deeper regions earth's crust are very hot. The temperature is so high that even rocks melt. If this heat is utilised as a source of energy, it is called geothermal energy.
Q.04:- What are the advantages of nuclear energy?
Ans:- The fission of an atom of uranium produces 10 million times the energy as produced by combustion of an atom of carbon from coil. Thus a large amount of energy can be tapped from nuclear fission. Many developed countries are already meeting more than 30% of their electrical power needs from nuclear reactors.
NCERT INTEXT QUESTIONS (PAGE NO. 253 Contd.)
Q.01:- Can any source of energy be pollution free? Why or why not?
Ans:- No source of energy can be pollution free because even if it is clean, its assembly could have caused environmental damage.
Q.02:- Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Ans:- Hydrogen is a cleaner fuel than CNG because it does not give carbon dioxide and also there is no fear of its insufficient combustion. However, it cannot be replaced for CNG till proper devices are developed for its use as a domestic fuel.
NCERT INTEXT QUESTIONS (PAGE NO. 254)
Q.01:- Name two energy sources that you would consider to be renewable.Give reasons for your choices.
Ans:- (ⅰ) Energy derived from bio-mass is a renewable source of energy because waste products are continuously produced. Plants and trees are also grown at all reasonable intervals.
(ⅱ) The energy derived from flowing water, wind, sun and ocean are renewable sources because these sources can be harnessed into energy so long as the present solar system exists.
Q.02:- Give the name of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Ans:- Fossil fuels like coal and petroleum are exhaustible sources of energy. The estimated reserves of these fuels are said to last us for about another 200 years while it takes millions of years for these to be produced.
