RBSE Class 10 Science Solutions Chapter 14 Sources of Energy

RBSE Class 10 Science Solutions Chapter 14 Sources of Energy

RBSE Class 10 Science Chapter 14 Sources of Energy InText Questions and Answers

Page 243.

Question 1.
What is a good source of energy?
Answer:
A good source of energy would be one:

• which would do a large amount of work per unit, volume or mass,
• which should be easily accessible,
• which should be easy to store and transport, and
• which should be economical.

Question 2.
What is a good fuel?
Answer:
A good fuel would be:

• easily available.
• optimum heat production per unit of volume mass used.
• should not produce a lot of smoke.
• should be cheap and easy to mantain.
• should not leave solid waste after combustion.
• should have low ignition temperature.
• calorific value of fuel should be high.

Question 3.
If you could use any source of energy for heating your food, which one would you use and why?
Answer:
We should use LPG or microwave oven to heat our food because

• It provides more energy per unit volume or per unit mass.
• They can be used easily.
• Their storage and transportation are easy.
• They do not cause any pollution.

Page 248.

Question 1.
What are the disadvantages of fossil fuels?
Answer:
Fossil fuels: These are the molecules of carbon. Compounds containing energy, which were originally created by vegetation using solar energy.
The disadvantages of using fossil fuels are as follows:

• They pollute the environment.
• They are non renewable source of energy.
• It takes million of years for the formation of fossil fuels and their reserves are limited.
• The oxides of carbon, sulphur and nitrogen released on burning are acidic oxides. Therefore, they cause acid rain, which also contaminants water and soil resources and causes respiratory diseases in humans and irritation in open organs of the body.

Question 2.
Why are we looking at alternate sources of energy?.
Answer:
As technology has developed, the energy consumption is also increasing. Every task in our life requires energy. For example: cooking, generating electricity and energy is required to run industries, which are being met from conventional energy sources. If conventional energy sources continue to be used at the current rate, then conventional sources will exhausted any day and this supply of energy will not be met by conventional energy sources. Therefore, we are attracted towards alternative sources of energy.

Question 3.
How has the traditional use of find and water energy been modified for our convenience?
Answer:
Water and wind are traditional sources of energy. Initially their energy use was very limited but nowadays due to technological development they are devloped as a main energy source.
Following improvements have been made in these:
(i) Wind energy is a pollution free energy source. Wind energy is converted into mechanical energy with the help of a windwill and it is being used in the production of electricity by mechanical works such as drawing water from a well and running an electric generator. For this large wind farms have been installed by putting several windmills together in places near seashore, where sufficient electric energy is produced.

(ii) Similarly, in ancient times, flowing water was commonly used for transportation, but now this energy is being used in various ways by converting it into hydroelectric energy by constructing dams. Electric energy is produced by flowing the water from the dams to the turbine, which is connected to the generators.

Page 253.

Question 1.
What kind of mirror concave, convex or plain would be best suited for use in a solar cooker? Why?
Answer:
A concave mirror is best suited for use in a solar cooker. A concave mirror concetrate solar radiation from a large area to small area of cooker, which increases the temperature and more heat is produced.

Question 2.
What are the limitations of the energy that can be obtained from the oceans?
Answer:
Following energies are obtained from sea, which have the following limitations
(i) Tidal Energy:
Tidal energy is harnessed by constructing a dam across a narrow opening to the sea. The locations where such dams can be built are limited.

(ii) Wave Energy:
Wave energy would be a viable proposition only where waves are very strong. Wave energy cannot be obtained from weak waves.

(iii) Ocean Thermal Energy Ocean Thermal-Energy Conversion Plants (OTEC) can operate if the temperature difference between the water at the surface and water at depths upto 2 km is 20 K (20° C) or more. The energy potential from the sea (tidal energy, wave energy and ocean thermal energy) is quite large, but efficient commercial exploitation is difficult.

Question 3.
What is geothermal energy?
Answer:
The heat energy inside the earth’s crust used to generate electricity is called geothermal energy.

Question 4.
What are the advantages of nuclear energy?
Answer:

1. This is a non conventional source , of energy.
2. Small amount of fuel (Uranium, Thorium etc.) produces a tremendous amount of energy.
3. In nuclear reactors once critical stage is achieved then it can function for a long time without use of any refulling.

Page 253.

Question 1.
Can any source of energy be pollution free? Why or why not?
Answer:
No, any source of energy cannot be pollution free, but the degree of pollution is different for different sources. For example: water from hydropower plant is polluted. In a thermal power plant, steam is generated by burning coal, which pollutes the air. Similarly waste from nuclear power stations produce harmful radiations. Only the actual operation of a device like the solar cell may be pollution free, but the assembly of the device would have caused some environmental damage. Thus, few sources causes pollution while generating energy while other cause pollution while the construction of a source. Thus no energy source is pollution free.

Question 2.
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Answer:
Yes, hydrogen is a cleaner fuel than CNG because CNG contains hydrocarbons. The carbon present in it is in the form of pollutants that form CO₂ upon burning of CNG. Whereas fusion of hydrogen does not create any kind of waste. Therefore, hydrogen is used as rocket fuel.

Page 254.

Question 1.
Name two energy sources that you would consider to be renewable. Give reasons for your choices.
Answer:
The two renewable energy sources are:
(a) Wind energy
(b) Water energy.

(a) Wind energy:
Wind energy is obtained from the wind blowing at a high speed. This air movement arises due to unequal heating of the landmass and water bodies by solar radiations. Since, the heating up of the landmass and water bodies depends on the sun. For this reason it is a renewable source of energy.

(b) Water energy:
The energy present in flowing water is called water energy. Since water in the reservoir would be refilled each time it rains and its is sun’s heat that cause clouds and rain. Therefore, water energy has been considered as a renewable source of energy.

Question 2.
Give the names of two energy sources that you would consider to be exhaustible. Give reasons for your choices.
Answer:
(i) Coal
(ii)Petroleum
(ii)Natural gas.

Above sources are present in limited amount because these fuels were formed over millions of years ago by vegetation and fauna being buried in the earth and will be exhausted soon if we continue to use them at present rate, so these are exhaustible.

RBSE Class 10 Science Chapter 14 Sources of Energy Textbook Questions and Answers

Question 1.
A solar water heater cannot be used to get hot water on
sunny day.
(b) a cloudy day.
(c) a hot day.
(d) a windy day.
Answer:
(b) a cloudy day.

Question 2.
Which of the following is not an example of a biomass energy source?
(a) wood
(b) gobargas
(c) nuclear energy
(d) coal
Answer:
(c) nuclear energy

Question 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?
(a) geothermal energy
(b) wind energy
(c) nuclear energy
(d) biomass.
Answer:
(a) geothermal energy

Question 4.
Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer:

Question 5.
Compare and contrast biomass and hydro-electricity .
Answer:

Question 6.
What are the limitations of extracting energy from:
(a) the wind?
(b) waves?
(c) tides?
Answer:
(a) Limitations of Wind Energy:

1. Wind energy farms can be established only at those places where wind blows for the greater part of a year. The wind speed should also be higher than 15km/h to maintain the required speed of the turbine.
2. Establishment of wind energy farms requires large area of land. For a 1MW generator, the farm needs about 2 hectares of land.
3. Since the tower and blades are exposed to the vagaries of nature like rain, sun, storm and cyclone, they need a high level of maintenance.

(b) Limitations of Wave Energy:

1. Wave is not available for power generation all the time.
2. It is expensive to install equipments to convert wave energy into electrical energy.
3. Waves are caused by high velocity oceanic winds. Only at few places, these winds are powerful that the energy associated with them can be exploited.

(c) Limitations of Tidal Energy:

1. There are only few sites available for dam construction.
2. Construction of dam in area of high tidal flow is a difficult task.

Question 7.
On what basis would you classify energy sources as
(a) renewable and non renewable?
(b) exhaustible and inexhaustible?
Are the options given in (a) and (b) the same?
Answer:
(a) Renewable and non renewable energy sources Renewable sources of energy are those which continue to be derived from nature. Such as water energy, wind energy, solar energy, etc. These sources can be used again and again, but those energy sources, which have limited reserves and which takes milions of years to restore, are called non-renewable energy sources. Such as coal, petroleum, natural gas, etc.

(b) Exhaustible and inexhaustible energy sources: Renewable sources of energy such as wind, water and solar energy, can be used again and again for a long time, therefore, they are called inexhaustible or renewable energy source. Conversely, if an energy source is exhausted after providing energy for a certain period of time and cannot be recovered, it is called exhaustible energy source. For example: fossil fuels. On the basis of the above facts we can say that the options of (a) and (b) are the same.

Question 8.
What are the qualities of an ideal source of energy?
Answer:
An ideal fuel should have the following qualities

1. which would do a large amount of work per unit volume or mass.
2. be easily accessible.
3. be easy to store and transport
4. be economical.

Question 9.
What are the advantages and disadvantages of using a solar cooker? Are there places where solar cookers would have limited utility?
Answer:
Advantages:

1. The expenses of cooking food through solar cooker are very less, because money is only spend in buying the cooker.
2. It does not cause any pollution due to non burning of fuel in it.

Disadvantages:

1. They do not work at night, in rainy and cloudy days.
2. Food cannot be made in short time, because solar cooker takes longer to cook.
3. The direction of the reflective mirror has to be changed repeatedly so that it remains in front of the Sun.

Places where solar cookers would have limited utility Yes, there are some areas where solar cookers have limited utility. For example: the use of solar cookers on the poles where the sun is not visible for half a year is limited. The use of solar cookers is very difficult in hilly areas where the sun’s rays remain for some time and quite oblique. Likewise, its use is limited in places where it is mostly cloudy.

Question 10.
What are the environmental consequences of the increasing demand for energy? What steps would you suggest to reduce energy consumption?
Answer:
The environmental consequences of the increasing demand for energy are Energy demand is continuously increasing with population growth. Energy is being obtained from any source, it have an adverse effect on the environment. Generally environmental consequences of the increasing demand for energy are as follows:

1. Due to increasing demand for energy, more sources of energy are being exploited, which creates an imbalance in the environment.
2. LPG and CNG which are considered as clear fuels, also pollute the environment due to extraction and transportation.
3. Burning fossil fuels causes air pollution, due to which the temperature of the earth is increasing rapidly.
4. The actual operation of a device like the solar cell may be pollution free, but the assembly of the device would have caused same environmental damages.

It is thus clear that increasing demand for energy is disturbing the environmental balance.
Steps to reduce energy consumption:

1. The misuse of energy should be stopped.
2. Equipment of low power consumption technology should be used.
3. Energy consumption can also be reduced by using alternative sources of energy.