Mix Examples - Sources of Energy Questions in English

(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, D) Option $C$ and $D$ are both scientifically correct statements. However,in the context of standard curriculum,both are often considered correct. Let's analyze them:
$1$. Nuclear waste disposal is a major environmental challenge due to radioactivity,making option $A$ incorrect.
$2$. Fossil fuels are finite resources that take millions of years to form,making option $B$ incorrect.
$3$. Hydro and wind energy are renewable and do not emit greenhouse gases during operation,making option $C$ correct.
$4$. The Sun provides a continuous supply of energy for billions of years,making it an inexhaustible source,which makes option $D$ correct.
Given the standard nature of such questions,both $C$ and $D$ are valid,but $D$ is often emphasized as the primary inexhaustible source.

(C) The incorrect statement is $C$.
Biogas is primarily composed of methane $(CH_4)$,not ethane.
Biogas burns without smoke and leaves behind no residual ash,making it a clean fuel.
Options $A$,$B$,and $D$ are scientifically correct statements regarding biomass and biogas production.

(N/A) Conventional sources of energy are those that have been used for a long time and are generally non-renewable,such as fossil fuels (coal,petroleum,natural gas) and thermal power plants.
Non-conventional sources of energy are those that are renewable and have been developed recently,such as solar energy,wind energy,tidal energy,and geothermal energy.
Harnessing Solar Energy: Solar energy is harnessed using solar cells (photovoltaic cells) that convert sunlight directly into electricity. $A$ solar cell is made of silicon and produces a small voltage when exposed to light. Many such cells are combined in a solar panel to generate sufficient power for domestic or industrial use.

(N/A) Yes,$I$ agree that the sun is the ultimate source of energy for most energy sources on Earth.
$1$. Fossil fuels: Coal,petroleum,and natural gas are formed from the remains of plants and animals that lived millions of years ago. These organisms grew by using solar energy through photosynthesis.
$2$. Wind energy: Wind is caused by the uneven heating of the Earth's surface by the sun,which creates pressure differences in the atmosphere.
$3$. Hydroelectric energy: The sun drives the water cycle by evaporating water from oceans,which later falls as rain or snow,filling reservoirs that power hydroelectric dams.
$4$. Biomass: Plants store solar energy in the form of chemical energy through photosynthesis,which is then utilized as biomass fuel.
Therefore,directly or indirectly,the sun is the primary source of almost all energy available to us.

(N/A) Biogas is a mixture of gases produced by the anaerobic degradation of biomass. Its primary component is methane $(CH_4)$.
Other constituents include:
$(i)$ Hydrogen $(H_2)$
$(ii)$ Hydrogen sulphide $(H_2S)$
$(iii)$ Carbon dioxide $(CO_2)$

(D) Renewable sources of energy are those that can be replenished naturally over a short period of time,such as $Solar$ energy,$Wind$ energy,or $Hydroelectric$ energy.
Non-renewable sources of energy are those that exist in limited amounts and cannot be replaced once consumed,such as $Coal$,$Petroleum$,or $Natural$ $gas$ $(CNG)$.

(N/A) The student may have made the following mistakes in the construction or operation of the solar cooker:
$(i)$ Not using a black-painted surface inside the box to absorb heat radiation.
$(ii)$ Using a plastic sheet instead of a glass sheet,which fails to trap heat effectively due to the greenhouse effect.
$(iii)$ Not using a plane mirror reflector to direct additional sunlight into the box.
$(iv)$ Using a non-black or reflective cooking vessel,which reduces the absorption of heat radiation.

(N/A) The floating gas holder type biogas plant is considered less advantageous for the following reasons:
$(i)$ The floating gas holder type biogas plant is expensive because it is constructed using steel.
$(ii)$ There is a higher risk of gas leakage due to potential defects in welding or the corrosion of the steel components over time.
$(iii)$ It requires frequent repairs and painting to prevent rust,which significantly increases its overall maintenance cost.

(D) Biomass,such as wood,has been used as a fuel for centuries,but it is inefficient and produces a lot of smoke.
In recent times,it has been modified to function as a more efficient fuel in the following ways:
$1$. By converting wood into charcoal,which burns without flames,is comparatively smokeless,and has a higher heat generation efficiency.
$2$. By processing biomass (like cow dung and plant waste) in a biogas plant to produce biogas (a mixture of methane,carbon dioxide,hydrogen,and hydrogen sulphide),which is an excellent,clean,and efficient fuel.

(N/A) $(i)$ $(a)$ It is cost-effective as solar energy is free of cost.
$(b)$ It is an eco-friendly method that causes no pollution.
$(ii)$ The phenomenon responsible for obtaining high temperature in a solar cooker is the $Greenhouse$ $effect$.
$(iii)$ The motivation behind using a solar cooker is to promote the use of non-conventional and renewable sources of energy,as fossil fuels are limited and non-renewable.

(N/A)

Energy from Biomass	Energy from Hydropower Plant
$(i)$ Biomass is a renewable and conventional source of energy.	$(i)$ Hydropower is also a renewable and conventional source of energy.
$(ii)$ Biomass can be utilized locally,reducing transportation costs.	$(ii)$ Hydropower requires large-scale infrastructure and transmission networks.
$(iii)$ Biomass utilization does not cause significant ecological imbalance or displacement of populations.	$(iii)$ Construction of large dams for hydropower often causes significant ecological imbalance and displacement of local populations.
$(iv)$ Biomass energy production is generally more decentralized and economical for rural areas.	$(iv)$ Hydropower plants involve high initial capital investment and are relatively costly to set up.

(N/A) $(i)$ The solar constant is approximately $1.4 \, kW/m^2$.
$(ii)$ $A$ plane mirror is used in a box-type solar cooker to reflect sunlight into the box.
$(iii)$ Hydrogen is difficult to use as a source of energy because: $(i)$ it is highly combustible and burns with an explosion,and $(ii)$ it has a very low ignition temperature,making it dangerous to store and transport.
$(iv)$ $A$ concave reflector-type solar cooker can attain temperatures up to about $200^{\circ}C$.
$(v)$ Fossil fuels are classified as non-renewable because they take millions of years to form and cannot be replenished once they are consumed.

(N/A) Biogas is a mixture of gases,primarily methane,$CO_2$,hydrogen,and hydrogen sulphide,produced by the anaerobic decomposition of organic matter.
Biogas is obtained by the anaerobic decomposition of cow dung (or other organic waste) in a biogas plant,which is a dome-like structure built with bricks.
The use of biogas is preferred over burning cow dung cakes because:
$(i)$ Biogas burns without smoke and does not cause air pollution,whereas burning cow dung cakes releases harmful smoke and pollutants.
$(ii)$ Biogas leaves no residue (ash) after combustion,whereas burning cow dung cakes leaves behind a significant amount of ash as residue.
$(iii)$ Biogas has a higher calorific value and is a more efficient fuel compared to cow dung cakes.

(N/A) The plane glass plate traps heat inside the box by preventing the escape of infrared radiation,which has a longer wavelength. This phenomenon is known as the greenhouse effect.
$(b)$ Solar energy causes the evaporation of water from oceans and other water bodies to form clouds. These clouds lead to precipitation (rain and snow) in mountainous regions. This water then flows into rivers,making the kinetic energy of river water an indirect form of solar energy.
$(c)$ The fission of ${}^{235}U$ is initiated by bombarding the nucleus with a slow-moving neutron. The ${}^{235}U$ nucleus absorbs this neutron to become ${}^{236}U$,which is highly unstable and immediately undergoes fission into smaller nuclei,releasing energy.

(N/A) $CNG$ is a non-renewable source of energy because it is a fossil fuel that takes millions of years to form and is present in limited quantities.
Hydrogen is a renewable source of energy because it can be produced from water through electrolysis and is virtually inexhaustible.
$(b)$ Hydrogen is considered a cleaner and better fuel than $CNG$ because:
$1$. Hydrogen combustion produces only water $(H_2O)$ as a byproduct, which is environmentally harmless.
$2$. $CNG$ combustion produces carbon dioxide $(CO_2)$, which is a greenhouse gas contributing to global warming, although it produces less pollution than coal or petroleum.

(N/A) When dams are constructed,large areas of vegetation are submerged. This submerged vegetation rots under anaerobic conditions,leading to the production of large amounts of methane,which is a potent greenhouse gas.
$(b)$ Technological inputs improve the efficiency of biomass fuels in the following ways:
$(i)$ Conversion of biomass into biogas in a biogas plant,which is a cleaner and more efficient fuel.
$(ii)$ Conversion of wood into charcoal by heating it in a limited supply of air (pyrolysis). Charcoal has a higher calorific value,burns without smoke,and is a more efficient fuel compared to raw wood.

(N/A) $(i)$ Efficient waste disposal from farms.
$(ii)$ Proper management and disposal of animal excreta.
$(iii)$ Production of biogas which can be used as a clean fuel in chulhas for cooking.
$(iv)$ The spent slurry acts as a nutrient-rich manure for the farms.
$(v)$ Biogas can be used for lighting in homes.
$(vi)$ It is an economical and sustainable source of energy.

(A) Aditya is taking the correct decision. The value exhibited by Aditya is environmental awareness and a sense of responsibility towards energy conservation.
$(b)$ Reasons for choosing a solar water heater:
$(i)$ $A$ solar water heater uses solar energy,which is a renewable and inexhaustible source of energy.
$(ii)$ It helps in saving electrical energy,which is often generated by burning fossil fuels. By reducing the consumption of electricity,it helps in lowering carbon emissions and mitigating global warming.

(N/A) The basic cause for winds to blow is the uneven heating of the Earth's surface by the Sun's energy.
Kanyakumari in Tamil Nadu is a prominent part of India where wind energy is commercially harnessed.
Comparison:
$(i)$ Both wind power and flowing water power are renewable and pollution-free sources of energy.
$(ii)$ Both involve the conversion of kinetic energy into mechanical energy (e.g.,rotating turbines) and subsequently into electrical energy.
$(iii)$ The power of flowing water is generally more consistent and concentrated compared to wind power,making it more efficient for large-scale electricity generation.
Hindrances in development:
$(i)$ Wind energy: It is intermittent and not available everywhere. Wind farms require specific locations with high wind speeds for most of the year.
$(ii)$ Water energy: The construction of large dams causes significant ecological damage,displaces populations,and is limited to specific geographical locations with perennial rivers.

(N/A) To overcome the problem of "limitation of sources of energy", we should prefer the use of alternative or non-conventional sources of energy such as solar energy, tidal energy, and wave energy.
$(b)$ Suggestions for the effective use of energy:
$1$. Switch off lights, fans, and other electrical appliances when not in use.
$2$. Use public transport or car-pooling to reduce fuel consumption.
$3$. Use energy-efficient appliances like $LED$ bulbs and $5$-star rated electrical devices.

(N/A) Scrap paper and vegetable waste can be used to produce biogas through anaerobic decomposition.
Converting these into biogas has the following advantages:
$(i)$ It produces a clean,cheap,and valuable fuel that serves as a sustainable energy source.
$(ii)$ It effectively manages waste by utilizing substances that would otherwise require significant space for landfilling or dumping.
$(iii)$ If this organic waste is left to decompose naturally in open dumps,it releases harmful greenhouse gases like methane and carbon dioxide,contributing to environmental pollution. Converting it into biogas prevents these emissions.

(A) The correct answer is $A$.
$Coal$, $Petroleum$, and $Lignite$ are all examples of fossil fuels, which are non-renewable sources of energy formed from the remains of ancient organisms over millions of years.
$Plants$ are a renewable source of energy (biomass) and are living organisms, making them fundamentally different from the fossilized fuels listed in the other options.

(B) The correct answer is $B$ (Gobar gas).
$1$. Coke,Bitumen,and Anthracite are all fossil fuel-based products or forms of coal.
$2$. Coke is a carbon-rich residue derived from coal.
$3$. Bitumen is a sticky,black,and highly viscous liquid or semi-solid form of petroleum.
$4$. Anthracite is a hard,compact variety of coal.
$5$. Gobar gas (biogas) is a renewable source of energy produced by the anaerobic decomposition of organic matter,whereas the others are non-renewable fossil fuel derivatives.