SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

SOURCES OF ENERGY

Class -10 Solutions for Science Chapter -14

PAGE – 243

1. What is a good source of energy?

Ans: A good source of energy fulfills the following criteria –

1.  It produces a lot of heat per unit mass.
2. It does a huge amount of work per unit mass.
3. It is easily accessible.
4. It is easy to store and transport.
5. It is economial.
6. It produces less amount of smoke.

2. What is a good fuel ?

Ans : Following should be the characterstics of a good fuel:

1. It should be fairly cheap.
2. It should be easily available.
3. Its ignition temperature should be reasonably above normal temperature.
4. It should not produce during burning any poisonous materials and irrigating fumes.
5. It should be conveniently handled and transported.
6. Its combustion rate should be steady and controlable.
7. It should not leave only residues or ash after burning.
8. It should burn in a way that can be controlled.

3. If you could use any source of energy for heating your food ,which one would you use and why?

Ans: We would prefer  to use cooking gas like LPG or CNG . It fulfills many of the criteria of a good fuel,most important like ignition temperature good calorific value and non pollution characteristics.

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

PAGE – 248

1. What are the disadvantages of fossil fuels?

Ans: The disadvantages of fossil fuels are –

1. Burning of coal and petroleum produces a lot of pollutants causing air pollution.
2. Fossil fuels release oxides of carbon, nitrogen , sulphar etc. that causes acid rain , which effects the soil fertility and potable water.
3. Burning of fossil fuels produces gases such as carbon dioxide that causes global warming.

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

2. Why are we looking at alternate sources of energy ?

Ans : The most important convenient and largely developed coventional source of energy are fossil fuels like petroleum,coal etc. Besides causing pollution problems,these sources are not renewable sources and with modern development and large scale usage their stocks are developing . We would thus in future have serious energy crisis. Therefore, it is urgently required to look for alternate source of energy.

3. How has the traditional use of wind and water energy been modified for convenience ?

Ans: i. Wind energy : Windmill forms are constructed at places where wind flows for greater part of the year at a speed greater than 15 km/ hr . The kinetic energy of the wind is converted into rotatory motion of windmill. Then the rotatory motion of the windmill is used to turn the turbine of electric generator.

ii. Water energy :  To use water energy for producing electricity a large number of high rise dams are constructed on the suitable river spots to construct 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 the falling water is converted into electrical energy.

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

PAGE- 253

1. What kind of mirror concave,convex or plain would be best suited for use in a solar cooker?Why?

Ans: A concave mirror is used in a solar cooker for this purpose because the mirror focuses all the incident sunlight at a point . The temperature at the point increases,thereby cooking and healing the food placed at that point.

2. What are the limitations of the energy that can be obtained from the oceans?

Ans: The forms of energy that can be obtained from ocean are tidal energy , wave energy ocean thermal energy.

There are several limitations in order to harness these energy –

1. Tidal energy depends on the relatively positioning of the earth,moon and sun .
2. High dams are required to be build to convert tidal energy into electricity.
3. Very strong waves are required to obtain electricity from wave energy.
4. To harness oceans thermal energy of efficiently the difference in the temperature of the surface water (hot) and the water to depth(cold) must be 20 c or more.

3. What is geothermal energy ?

Ans: The interior or desper regions of earth’s crust are very hot ,the temperature is so high that even rocks melt,if this heat is utilized as a source of energy it is called geothermal energy.

4. What are the advantages of nuclear energy ?

Ans: The advantages of nuclear energy are as follows –

1. Large amount of energy is produced per unit mass.
2. It does not produce smoke.It is a clean energy.
3. Fission of 1 atom of uranium produces 10 million times the energy released by burning of atom of carbon.
4. Fission of four hydrogen atoms,produces huge amount of energy approx equal to 27 (Megaelectronvolt) MeV

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

PAGE-253

1. Can any source of energy be pollution free? Why or why not?

Ans:   Yes, there can be source of energy that can be pollution free in using it e.g. sun’s energy that is used in solar cooker , solar water heater , solar cell panels.

2. 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.

PAGE – 254

1. Name two energy sources that you would consider to be renewable. Give reasons for your choice.

Ans:

1. Energy derived from biomass is a remarkable source of energy because waste product are continuously produced . Plants and trees are also grown at all reasonable intervals.
2. The energy derived from the flowing water , wind , sun and oceans are renewable sources because these sources can be harvested into energy so long as the present solar system exits.

2. Give the names 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.

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

TEXTBOOK EXERCISES

PAGE – 254

1. A  solar water heater can not be used to hot water on

1. A sunny day
2. A cloudy day
3. A hot day
4. A windy day

Ans:b. A cloudy day

2. Which of the  following is not  an example of a bio mas source?

1. Wood
2. Gobar gas
3. Nuclear energy
4. Coal

Ans: c. Nuclear energy

3. Most of the sources of energy we use represent stored solar energy.Which of the following is not ultimately derived from the sun’s energy?

1. Geothermal energy.
2. Wind energy
3. Nuclear energy
4. Bio mass

Ans: c. Nuclear energy

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

4. Compare and contrast fossil fuels and the sun as direct sources of energy.

Ans:

Fossil fuel	Sun
i. It is non – renewable	i. It is renewable
ii. It causes pollution in the environment.	ii. It does not cause pollution.
iii. It is expensive , not easily available any time and anywhere.	iii. It is cheap , easily available for most of the time and at most of the places.

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

5. Compare and contrast biomass and hydroelectricity as sources of energy.

Ans:

Biomass	Hydroelectricity
i. It causes pollution.	i. It does not cause pollution.
ii. It is cheap and easily available.	ii. It is expensive and not easily available.
iii. Initial cost for forming the energy bio-gas plant is very cheap,maintenance is also cheap.	iii. The initial cost of building the power plant is expensive, its maintenance is also expensive.

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

6. What are the limitations of extracting energy from –

1. The wind
2. Wave
3. tides

Ans: a. Limitations of wind energy:

1. need a large ope space to couple a number of wind mills.
2. can be tapped only during specific periods when the wind speed is above 15 km/h
3. wear an tear of wind mill parts is quite high.

b. Limitations of wave energy :

1. The place and time is limited when the waves are strong.
2. Initial setup cost is expensive.
3. Efficiency is low.

c. Limitations of tides energy:

1. The areas where tidal energy can be harnessed is less.
2. The efficiency is very low.
3. The plants are not cost effective.

7. On what basis would you classify energy sources as

1. renewable and non renewable
2. exhaustible and inexhaustible

Are the options given in (a) and (b) the same?

Ans: Both (a) and (b) option are same

 

Renewable/Inhaustible	Non-renewable/Exhaustible
i. They are also called exhaustible	i. They are called as exhaustible
ii. The energy source that will not finish and can be renewed or made again is called renewable source of energy e.g sun, wind , water	ii. The energy source that will finish and will get exhausted and can not be made very soon or takes million of years for its formation e.g fossil fuels, petrol, coal

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

8. What are the qualities of an ideal source of energy?

Ans: An ideal source of energy:

1. must give an adequate amount of heat energy.
2. must be convenient to use so as to give energy at a steady rate.
3. must be easy to store and transport.
4. It should not cause any environmental pollution.

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

9. What are the advantages and disadvantages of using a solar cooker?

Are there places where solar cookers would have limited utility?

Ans: Advantage of solar cooker:

a. it is cheap and easy to handle.

b. It is pollution free heating device.

Disadvantage of solar cooker:

a. It is very slow, takes long time for cooking.

b. Solar cookers do not work on a cloudy day.

c. The reflectors position need to be monitored so as it reflects the sunlight at the centre focused point of the solar  cooker.

Yes, the places where sun’s energy is not sufficient ,the use of solar cookers would be limited.

10. What are the environmental consequences of the increasing demand for energy? what steps would you suggest to reduce energy consumption?

Ans: No matter what source of energy is used , increasing demand would disturb the environment in some way or the other.either it would cause more pollution or cause environmental damage. Development and consumption of energy would go together.therefore we should concentrate more on finding better and alternative sources of energy.when looking for alternative sources ,the following  points should be kept in mind.

i. Ease and cost of extracting energy.

ii. The efficient of the available technology.

iii. Environmental impact of using that sources.

 

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

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SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

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SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14

SOURCES OF ENERGY Class -10 Solutions for Science Chapter -14