Textbook - Sources of Energy Questions in English

(C) good source of energy fulfills the following criteria:
$(I)$ It produces a large amount of heat per unit mass.
$(II)$ It performs a significant amount of work per unit mass.
$(III)$ It is easily accessible.
$(IV)$ It is easy to store and transport.
$(V)$ It is economical.
$(VI)$ It produces minimal smoke and pollution.

(B) good fuel is defined by several key characteristics:
$1$. It should have a high calorific value,meaning it produces a huge amount of heat upon burning.
$2$. It should be easily available and affordable.
$3$. It should be easy to store and transport.
$4$. It should burn cleanly,producing minimal smoke or harmful gases.
$5$. It should have a moderate ignition temperature,making it safe to handle.

(C) Natural gas is the preferred source of energy for heating and cooking food because it is a clean source of energy.
It does not produce a significant amount of smoke or pollutants upon combustion.
Although it is highly inflammable,it is convenient to use,easy to transport through pipelines,and it releases a large amount of heat energy when burned,making it highly efficient.

(D) The disadvantages of fossil fuels are as follows:
$(a)$ Burning of coal and petroleum produces a large amount of pollutants,causing air pollution.
$(b)$ Fossil fuels release oxides of carbon,nitrogen,and sulphur,which cause acid rain. This acid rain negatively affects soil fertility and the quality of potable water.
$(c)$ Burning of fossil fuels releases greenhouse gases such as carbon dioxide,which leads to global warming.

(B) Fossil fuels,which have been traditionally used by human beings as energy sources,are non-renewable sources of energy.
These sources of energy are limited and cannot replenish on their own.
They are being consumed at a very high rate.
If this rate of consumption continues,then the fossil fuels would be exhausted from the Earth.
Therefore,we have to conserve these energy sources and look for alternate sources of energy.

(N/A) Traditionally,waterfalls were used as a source of potential energy,which was converted into electricity with the help of turbines. Since waterfalls are limited,large-scale water dams have been constructed. Nowadays,hydroelectric dams are used to harness the potential energy of stored water. In these dams,water falls from a height onto a turbine,which rotates to produce electricity.
Earlier,windmills were primarily used to perform mechanical work,such as drawing water from a well or grinding grain. Today,modern windmills (wind turbines) are used to generate electricity. In these systems,the kinetic energy of the wind is harnessed to rotate the blades,which in turn rotate the turbine of an electric generator to produce electricity.

(A) solar cooker uses the heat of sunlight to cook and heat food. $A$ mirror is used to reflect and focus sunlight at a single point. $A$ concave mirror is best suited for this purpose. The concave mirror converges all the incident parallel rays of sunlight at its focus. This concentration of light energy significantly increases the temperature at that point,which is used to cook or heat the food placed there.

(N/A) The forms of energy that can be obtained from the ocean are tidal energy,wave energy,and ocean thermal energy. There are several limitations in order to harness these energies.
$(i)$ Tidal energy depends on the relative positioning of the Earth,the moon,and the Sun.
$(ii)$ High dams are required to be built to convert tidal energy into electricity.
$(iii)$ Very strong waves are required to obtain electricity from wave energy.
$(iv)$ To harness ocean thermal energy efficiently,the difference in the temperature of surface water (hot) and the water at depth (cold) must be $20\,^{\circ}C$ or more.

(B) Geothermal power plants use the heat of the Earth to generate electricity. This heat energy of the Earth is known as geothermal energy.
When there are geological changes,the molten rocks present in the core of the Earth are pushed to the Earth's crust. This forms regions of hot spots. Steam is generated when the underground water comes in contact with these hot spots,forming hot springs. This trapped steam is used to generate electricity in geothermal power plants.

(N/A) The advantages of nuclear energy are as follows:
$(a)$ A large amount of energy is produced per unit mass.
$(b)$ It does not produce smoke, making it a clean source of energy.
$(c)$ The fission of one atom of uranium produces $10$ million times the energy released by the burning of one atom of carbon.
$(d)$ The fusion of four hydrogen atoms produces a huge amount of energy, approximately equal to $27 \, \text{MeV}$.

(N/A) No source of energy can be considered truly pollution-free.
While some sources like solar cells are often labeled as pollution-free,their manufacturing process causes indirect environmental damage.
Similarly,in the case of nuclear fusion,although the fusion reaction itself does not produce radioactive waste,the process requires an extremely high temperature of approximately $10^7\, K$.
This temperature is typically achieved through nuclear fission reactions,which generate highly hazardous radioactive waste.
Therefore,considering the entire lifecycle and the processes involved,no source of energy is completely pollution-free.

(A) Yes,hydrogen is considered a cleaner fuel than $CNG$.
$CNG$ (Compressed Natural Gas) consists of hydrocarbons,which contain carbon.
When $CNG$ burns,it releases carbon-based pollutants like carbon dioxide and other greenhouse gases into the atmosphere.
In contrast,hydrogen combustion produces only water $(H_2O)$ as a byproduct.
Since hydrogen combustion does not produce carbon-based pollutants or harmful emissions,it is environmentally cleaner than $CNG$.

(N/A) Two renewable sources of energy are as follows:
$(a)$ Sun: The energy derived from the Sun is known as solar energy. Solar energy is produced by the fusion of hydrogen into helium and other heavy elements. $A$ large amount of hydrogen is present in the Sun,allowing it to replenish on its own. The Sun is expected to continue burning for another $5$ billion years. Hence,solar energy is a renewable source of energy.
$(b)$ Wind: Wind energy is derived from air blowing at high speeds. Wind energy is harnessed by windmills to generate electricity. Wind is caused by the uneven heating of the Earth's surface by the Sun. Since this heating process will continue as long as the Sun exists,wind energy will remain available indefinitely.

(N/A) Two exhaustible energy sources are as follows:
$(a)$ Coal: It is produced from the dead remains of plants and animals that have remained buried under the Earth's crust for millions of years. It takes millions of years to form coal. Industrialization has increased the demand for coal. However,coal cannot replenish within a short period of time. Hence,it is a non-renewable or exhaustible source of energy.
$(b)$ Wood: It is obtained from forests. Deforestation at a rapid rate has caused a significant reduction in the number of forests on the Earth. It takes hundreds of years for a forest to grow. If deforestation continues at this rate,there will be no wood left on the Earth. Hence,wood is an exhaustible source of energy.

(C) solar water heater uses solar energy to heat water.
It requires bright and intense sunlight to function properly.
On a cloudy day,the sunlight is blocked by clouds and is unable to reach the solar collector effectively.
Therefore,sufficient solar energy is not available for the solar heater to work.
Hence,a solar water heater cannot be used to get hot water on a cloudy day.

(D) Bio-mass is a source of energy that is obtained from plant materials and animal wastes.
Nuclear energy is released during nuclear fission and fusion processes.
In nuclear fission,a uranium atom is bombarded with low-energy neutrons,causing it to split into two relatively lighter nuclei,which releases a huge amount of energy.
In nuclear fusion,lighter nuclei are fused together to form a relatively heavier nucleus,which also produces a tremendous amount of energy.
Therefore,nuclear energy is not an example of a bio-mass energy source.
Wood is a plant material,gobar gas is formed from animal dung,and coal is a fossil fuel obtained from the buried remains of plants and animals; hence,these are all bio-mass products.

(A) Nuclear energy is released during nuclear fission and fusion. In nuclear fission,a uranium atom is bombarded with low-energy neutrons,causing it to split into two relatively lighter nuclei,which releases a huge amount of energy.
In nuclear fusion,lighter nuclei are fused together to form heavier nuclei,also releasing tremendous energy.
These reactions occur independently of sunlight.
Geothermal energy,wind energy,and bio-mass are all ultimately derived from solar energy.
Geothermal energy is heat stored within the Earth's crust,partially influenced by solar heating of the atmosphere and oceans.
Wind energy is caused by the uneven heating of the Earth's surface by the Sun.
Bio-mass is derived from plants and animal wastes,which grow and develop through photosynthesis,a process directly dependent on sunlight.

(N/A) Fossil fuels are energy sources,such as coal and petroleum,obtained from underneath the Earth's crust. They are directly available to human beings for use. Hence,fossil fuels are a direct source of energy. These are limited in amount.
These are non-renewable sources of energy because they cannot be replenished in nature. Fossil fuels take millions of years for their formation. If the present fossil fuel reserves of the Earth get exhausted,their formation will take millions of years.
Fossil fuels are also very costly.
On the other hand,solar energy is a renewable and direct source of energy. The Sun has been shining for several billion years and will continue to do so for the next $5$ billion years.
Solar energy is available free of cost to all in unlimited amounts. It is continuously replenished by the nuclear fusion reactions occurring within the Sun itself.

(N/A) Bio-mass and hydro-electricity are both renewable sources of energy.
Bio-mass is derived from organic matter such as dead plants and animal wastes. It is replenished through natural biological processes. Examples include wood,agricultural residues,and gobar gas.
Hydro-electricity is generated from the potential energy stored in water at a height. It is harnessed through mechanical processes involving turbines and generators. Unlike bio-mass,which is chemical energy,hydro-electricity is a form of mechanical energy conversion.

(C) Wind energy is harnessed using windmills.
One of the primary limitations is that a windmill requires a minimum wind speed of more than $15 \,km/h$ to generate electricity effectively.
Additionally,to generate a significant amount of power,a large number of windmills are required,which necessitates a vast land area for the establishment of wind farms.

(D) The primary limitation of extracting energy from ocean waves is that it requires very strong and consistent ocean waves to be economically and technically viable.
Additionally,the technology for harnessing wave energy is still in the developmental stage,making the installation and maintenance costs very high.
Furthermore,these power plants can only be set up in specific coastal locations where wave intensity is sufficient.

(D) The limitations of extracting energy from tides are as follows:
$1$. It requires very high tides to generate a significant amount of energy,which are not available everywhere.
$2$. The occurrence of tides is dependent on the relative positions of the Sun,the Moon,and the Earth,making the energy supply intermittent and not constant.

(A) The source of energy that replenishes in nature is known as a renewable source of energy. Sun,wind,moving water,and biomass are some examples of renewable sources of energy.
The source of energy that does not replenish in nature is known as a non-renewable source of energy. Coal,petroleum,and natural gas are some examples of non-renewable sources of energy.
$(b)$ Exhaustible sources are those sources of energy that will deplete and exhaust after a few hundred years. Coal and petroleum are examples of exhaustible sources of energy.
Inexhaustible sources of energy are those that will not exhaust in the future. These are unlimited. Solar energy and wind energy are examples of inexhaustible sources of energy.
Yes,the categories given in $(a)$ and $(b)$ are essentially the same.

(N/A) An ideal source of energy must possess the following qualities:
$I.$ It should be economical and easily accessible.
$II.$ It should be easy to store and transport.
$III.$ It should perform a large amount of work per unit mass or volume.
$IV.$ It should be safe to handle and use.
$V.$ It should be smoke-free and cause minimal pollution.

(N/A) Advantages of a solar cooker:
$1$. It uses solar energy,which is an inexhaustible,clean,and renewable source of energy.
$2$. Solar energy is free and available in unlimited amounts,making the operation of a solar cooker cost-effective.
$3$. It does not cause any environmental pollution.
Disadvantages of a solar cooker:
$1$. The initial cost of purchasing a solar cooker can be high.
$2$. It does not work without direct sunlight. Therefore,it is ineffective on cloudy days or during the night.
$3$. Cooking food in a solar cooker is a slow process compared to conventional methods.
Places with limited utility:
Solar cookers have limited utility in regions where days are very short,or in areas that experience heavy cloud cover or frequent rainfall throughout the year,as they rely entirely on solar radiation.

(N/A) The environmental consequences of the increasing demand for energy include:
$1$. Depletion of non-renewable resources like fossil fuels ($coal$, $petroleum$, $natural \ gas$).
$2$. Increased emission of greenhouse gases ($CO_2$, $CH_4$) leading to global warming and climate change.
$3$. Air pollution due to the release of harmful gases ($SO_2$, $NO_x$) and particulate matter.
$4$. Habitat destruction and ecological imbalance due to large-scale mining and dam construction.
Steps to reduce energy consumption:
$1$. Use electrical appliances efficiently and switch them off when not in use.
$2$. Adopt energy-efficient technologies like $LED$ bulbs and $star-rated$ appliances.
$3$. Promote the use of public transport to reduce fuel consumption.
$4$. Utilize renewable sources of energy such as solar, wind, and hydroelectric power.
$5$. Practice the $3R$ principle: Reduce, Reuse, and Recycle.