Mix Examples - Sources of Energy Questions in English

(A) non-renewable source of energy is one that exists in limited amounts and cannot be replaced once it is consumed,or takes millions of years to form.
Fossil fuels (such as coal,petroleum,and natural gas) are formed from the remains of ancient plants and animals over millions of years.
Once these are exhausted,they cannot be replenished within a human timescale.
In contrast,the Sun,wood (biomass),and wind are considered renewable sources because they are naturally replenished or are continuously available.

(B) Acid rain is primarily caused by the emission of sulfur dioxide $(SO_2)$ and nitrogen oxides $(NO_x)$ into the atmosphere.
These gases are released during the combustion of fossil fuels such as coal,oil,and natural gas in power plants,industries,and vehicles.
When these gases react with water vapor,oxygen,and other chemicals in the atmosphere,they form sulfuric acid $(H_2SO_4)$ and nitric acid $(HNO_3)$.
These acids then fall to the ground with rain,snow,or fog,resulting in acid rain.

(C) Thermal power plants are designed to generate electricity by heating water to produce steam.
This steam is then used to rotate turbines,which drive generators.
To produce the heat required to boil the water,fossil fuels such as coal,petroleum,or natural gas are burned.
Therefore,fossil fuels are the primary fuel source used in thermal power plants.

(D) In a hydro power plant,water is stored at a height in a dam,which gives it a large amount of potential energy.
When this water is allowed to fall,its potential energy is converted into kinetic energy.
This kinetic energy of the flowing water is then used to rotate the turbines of the generator,which ultimately converts the mechanical energy into electricity.
Therefore,the primary energy conversion process involves the conversion of potential energy stored in water into electricity.

(A) The $Sun$ is the ultimate source of energy for almost all life forms on $Earth$.
Solar energy is captured by plants through photosynthesis to produce chemical energy (food).
This energy is then transferred through food chains to other organisms.
Additionally, fossil fuels like coal and petroleum are essentially stored solar energy from ancient plants and animals.
Therefore, the $Sun$ is considered the primary and ultimate source of energy.

(B) Solar energy is considered the cleanest form of energy because it is a renewable resource that does not emit greenhouse gases or pollutants during its harnessing and utilisation.
Nuclear energy,while low in carbon emissions,produces radioactive waste that is difficult to manage.
Thermal energy (typically from fossil fuels) releases significant amounts of $CO_2$ and other pollutants.
Geothermal energy is cleaner than fossil fuels but can release small amounts of gases like hydrogen sulfide from underground reservoirs.

(C) Ocean thermal energy conversion $(OTEC)$ plants operate on the principle of the temperature difference between the warm surface waters of the ocean and the colder deep waters.
At the surface,the water is heated by solar radiation,while the water at depths of $2 \ km$ or more is significantly colder.
This temperature gradient is used to operate a heat engine,which produces electricity.
Therefore,ocean thermal energy is specifically due to the temperature difference at different levels in the ocean.

(D) The major challenge in harnessing nuclear energy is the safe disposal of spent fuel (nuclear waste).
Nuclear waste remains radioactive and hazardous for thousands of years,posing significant environmental and health risks if not managed properly.
While splitting nuclei (fission) and sustaining the chain reaction are technical challenges,they have been successfully achieved in nuclear reactors.
Converting nuclear energy into electrical energy is also a standard process using steam turbines.
Therefore,the most critical long-term problem is the safe storage and disposal of radioactive waste.

(A) The glass sheet of a solar cooker is responsible for the greenhouse effect.
When solar radiation (short-wavelength infrared rays) enters the box through the glass sheet,it is absorbed by the black-coated interior.
The interior then emits long-wavelength infrared radiation (heat).
The glass sheet prevents this heat from escaping the box,trapping it inside and thereby increasing the temperature,which is the principle of the greenhouse effect.

(B) Biogas is a mixture of gases produced by the breakdown of organic matter in the absence of oxygen (anaerobic digestion).
It primarily consists of $CH_4$ (methane),which typically accounts for $50-75\%$ of the total volume.
Other components include $CO_2$ (carbon dioxide),$H_2$ (hydrogen),and $H_2S$ (hydrogen sulphide) in smaller quantities.
Therefore,methane is the main constituent of biogas.

(C) The power generated by a windmill is directly proportional to the cube of the wind velocity $(P \propto v^3)$.
As the wind speed increases,the kinetic energy of the air hitting the blades increases significantly,leading to higher power output.
While other factors like blade area and air density play a role,wind velocity is the most critical variable in determining the power output of a wind turbine.

(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.

(A) In a hydroelectric power plant,the potential energy of water stored at a height is converted into kinetic energy as it falls.
According to the formula for gravitational potential energy,$PE = mgh$,where $m$ is the mass of water,$g$ is the acceleration due to gravity,and $h$ is the height.
As the height $h$ increases,the potential energy of the water increases.
When this water falls,this higher potential energy is converted into a larger amount of kinetic energy,which in turn rotates the turbine more efficiently to generate more electrical power.

(A) Wind power is harnessed by placing windmills in open spaces where wind blows at high speeds. Therefore,the statement that it is expected to harness wind power to a minimum in open space is incorrect. Windmills are specifically designed to be placed in open areas to maximize the capture of kinetic energy from the wind. The source of wind power is the kinetic energy of moving air,not potential energy. The rotation of the blades is used to drive a turbine,which in turn generates electricity.

(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) The need to harness non-conventional sources of energy arises due to the following reasons:
$(i)$ The demand for energy is continuously increasing due to the improvement in the quality of life and the rapid growth of the human population.
$(ii)$ Conventional sources of energy,such as fossil fuels,are limited in nature and are being depleted at a fast rate,making them unsustainable for the long term.

(N/A) Two different ways of harnessing energy from the ocean are:
$1$. Tidal Energy: This is generated by utilizing the rise and fall of ocean water levels due to the gravitational pull of the moon and the sun. Dams are constructed across narrow openings of the sea to trap water during high tide and release it during low tide to rotate turbines.
$2$. Wave Energy: This is harnessed by capturing the kinetic energy of ocean waves. Various devices are used to convert the oscillating motion of waves into mechanical energy, which then drives a generator to produce electricity.
$3$. Ocean Thermal Energy Conversion $(OTEC)$: This method utilizes the temperature difference between the warm surface water of the ocean and the colder deep water to run a heat engine and generate electricity.

(D) To minimise environmental pollution caused by the burning of fossil fuels,the following steps can be taken:
$(i)$ Use of smokeless appliances: These devices ensure more efficient combustion,reducing the release of harmful gases and particulate matter.
$(ii)$ Afforestation: Planting more trees helps in absorbing $CO_2$ from the atmosphere,thereby mitigating the greenhouse effect.
$(iii)$ Transition to renewable energy: Shifting towards solar,wind,and hydroelectric power reduces reliance on fossil fuels.
$(iv)$ Proper maintenance of vehicles: Regular servicing of engines ensures efficient fuel combustion and lower emissions.

(N/A) $1$. The plane mirror acts as a reflector that reflects sunlight into the box of the solar cooker,thereby increasing the intensity of solar radiation falling on it.
$2$. The glass sheet allows short-wavelength solar radiation to enter the box but prevents long-wavelength infrared radiation (heat) from escaping,thus trapping the heat inside. This phenomenon is known as the greenhouse effect,which helps in raising the temperature inside the cooker.

(N/A) $(i)$ Solar cells have no moving parts.
$(ii)$ They require very little maintenance.
$(iii)$ They can be set up in remote and inaccessible areas where laying power transmission lines is difficult or expensive.

(N/A) Biomass refers to the organic matter produced by plants and animals,such as agricultural waste,wood,cow dung,and sewage. It is a renewable source of energy.
To obtain bio-energy from biomass,it can be processed in a biogas plant. In this process,biomass (like cow dung and plant waste) is mixed with water to form a slurry and fed into a digester tank. In the absence of oxygen (anaerobic conditions),microorganisms decompose the organic matter,producing biogas (primarily methane). This gas is then collected and used as a fuel for cooking or lighting. The remaining slurry is used as high-quality manure.

(C) The limitations of wind energy are as follows:
$1$. Wind speed is erratic and not constant,which means energy cannot be harnessed continuously.
$2$. Wind farms require very large areas of land to be effective.
$3$. The initial cost of setting up wind turbines is high.

(A) The process used to harness nuclear energy in modern power plants is $Nuclear Fission$.
$1$. In this process,the nucleus of a heavy atom like $Uranium-235$ is bombarded with low-energy neutrons.
$2$. The nucleus splits into smaller,lighter nuclei,releasing a tremendous amount of energy in the form of heat.
$3$. This heat is used to boil water into steam,which then drives a turbine to generate electricity.
$4$. The process also releases more neutrons,which sustain a $Chain Reaction$.
$5$. Finally,the radioactive waste generated must be carefully stored and disposed of to prevent environmental contamination.

(N/A) Solar energy can be harnessed using devices like solar cookers,solar water heaters,and solar cells. Solar cookers and heaters use reflectors to concentrate sunlight,while solar cells convert solar energy directly into electricity.
Limitations of using solar energy:
$1$. It is only available during the daytime and is less effective on cloudy or rainy days.
$2$. Solar energy devices require large surface areas for installation and can be expensive to set up initially.
Overcoming these limitations:
$1$. To address the issue of availability,energy storage systems like batteries are used to store electricity generated by solar cells for use during the night or cloudy days.
$2$. Research into advanced materials and mass production of solar cells is helping to reduce costs and improve efficiency,making solar energy more accessible.

(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) The need for harnessing non-conventional sources of energy arises because:
$1$. Fossil fuels are finite and are depleting rapidly due to high consumption.
$2$. The global population is increasing, leading to a higher demand for energy.
$3$. There is a need to improve the quality of life and reduce environmental pollution caused by burning fossil fuels.
Energy can be harnessed from the sea in the following ways:
$1$. Tidal Energy: This is harnessed by constructing dams across a narrow opening to the sea. The rise and fall of sea levels during high and low tides rotate turbines to generate electricity.
$2$. Wave Energy: This is harnessed by trapping the kinetic energy of waves near the seashore to rotate turbines or drive other mechanisms.
$3$. Ocean Thermal Energy Conversion $(OTEC)$: This utilizes the temperature difference between the warmer surface waters of the ocean and the colder deep waters to operate heat engines and generate electricity.

(N/A) Environmental consequences of using fossil fuels include:
$1$. Air pollution: Burning fossil fuels releases harmful gases like $CO_2$,$SO_2$,and $NO_2$,which cause respiratory problems and smog.
$2$. Greenhouse effect: Increased levels of $CO_2$ lead to global warming and climate change.
$3$. Acid rain: $SO_2$ and $NO_2$ react with water vapor to form acids,which damage buildings,soil,and aquatic life.
Steps to minimize pollution:
$1$. Use of efficient and smokeless appliances (e.g.,improved chulhas).
$2$. Adoption of refined technology to reduce emissions from power plants.
$3$. Judicious and efficient use of energy to reduce overall demand.
$4$. Promoting the use of non-conventional sources of energy like solar,wind,and hydroelectric power,which have a minimal environmental footprint.

(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) Biomass refers to the organic matter produced by plants and animals,such as agricultural residues,cow dung,and wood,which serves as a renewable source of energy.
Principle: $A$ biogas plant operates on the principle of anaerobic fermentation. In the absence of oxygen,microorganisms break down complex organic matter (biomass) into simpler substances,releasing gases like methane $(CH_4)$,carbon dioxide $(CO_2)$,hydrogen $(H_2)$,and hydrogen sulfide $(H_2S)$.
Working:
$1$. $A$ mixture of cow dung and water (slurry) is prepared in the mixing tank and fed into the digester.
$2$. The digester is a sealed,oxygen-free tank where anaerobic bacteria decompose the biomass.
$3$. As decomposition occurs,biogas is produced and collects in the gas holder (dome) above the slurry.
$4$. The pressure of the accumulated gas pushes the spent slurry into the overflow tank,which is then removed and used as high-quality manure.
$5$. The biogas is supplied to homes through pipes for cooking and lighting.

(N/A) The two common nuclear fuels used for the process of nuclear fission are $Uranium-235$ $(U-235)$ and $Plutonium-239$ $(Pu-239)$. $Thorium-232$ is also used as a fertile material in nuclear reactors.

(N/A) The energy released during the nuclear fission of a single uranium atom is approximately $10$ million times greater than the energy released during the combustion of a single carbon atom from coal.

(N/A) The two conventional sources of energy are:
$(i)$ Fossil fuels (such as coal,petroleum,and natural gas).
$(ii)$ Hydro power (energy derived from flowing water).

(N/A) The two non-conventional sources of energy are:
$(i)$ Geothermal energy
$(ii)$ Nuclear energy

(N/A) Fossil fuels are considered a nonrenewable source of energy because they take millions of years to form through natural geological processes. Once these limited reserves are consumed,they cannot be replenished within a human timescale.

(N/A) The two primary factors that cause winds to blow are:
$1$. Unequal heating of the Earth's surface by solar radiation: Different parts of the Earth (landmasses and water bodies) absorb solar energy at different rates,leading to temperature differences.
$2$. Rotation of the Earth: The Earth's rotation creates the Coriolis effect,which influences the direction and movement of air masses,contributing to the formation of wind patterns.

(N/A) To generate electric power using a windmill,the wind speed must be higher than $15 \, km/h$. This minimum velocity is necessary to overcome the inertia of the blades and the internal friction of the generator system to produce a useful amount of electricity.

(B) Acid rain is primarily caused by the emission of acidic oxides such as sulphur dioxide $(SO_2)$,nitrogen oxides $(NO_x)$,and carbon dioxide $(CO_2)$ into the atmosphere.
These gases are released mainly through the burning of fossil fuels,industrial processes,and vehicular emissions.
When these gases react with water vapor in the atmosphere,they form acids like sulphuric acid $(H_2SO_4)$,nitric acid $(HNO_3)$,and carbonic acid $(H_2CO_3)$.
These acids then dissolve in rainwater,lowering its $pH$ and resulting in acid rain.

(N/A) The microorganisms involved in biogas production are known as methanogens or anaerobic bacteria.
$1$. These microorganisms function in the absence of oxygen,a process known as anaerobic respiration.
$2$. They decompose complex organic matter,such as animal dung and agricultural waste,into simpler substances.
$3$. During this decomposition process,they release a mixture of gases,primarily methane $(CH_4)$,carbon dioxide $(CO_2)$,hydrogen $(H_2)$,and hydrogen sulfide $(H_2S)$,which is collectively known as biogas.

(N/A) The two primary combustible components of biogas are methane $(CH_{4})$ and hydrogen $(H_{2})$. These gases are produced during the anaerobic decomposition of organic matter and contribute significantly to the calorific value of biogas.

(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 $(CO_2)$

(N/A) biogas plant is considered a safe and efficient method of waste disposal for the following reasons:
$1$. It effectively manages organic waste,such as animal dung and agricultural residues,by converting them into useful energy.
$2$. The process produces biogas,which is a clean fuel that burns without smoke and leaves no harmful residue,thereby reducing air pollution.
$3$. The remaining slurry,after the production of biogas,is rich in nitrogen and phosphorus,making it an excellent organic manure for crops.
$4$. It helps in maintaining sanitation by disposing of waste in a controlled environment,which prevents the breeding of pathogens.

(N/A) Most thermal power plants are established near coal or oil fields because the transmission of electricity through power lines is significantly more efficient and cost-effective than transporting heavy fossil fuels like coal and petroleum over the same distance.

(N/A) The two elements commonly used in the fabrication of solar cells are:
$(i)$ Silicon $(Si)$: It is the primary semiconductor material used to form the $p-n$ junction in photovoltaic cells.
$(ii)$ Silver $(Ag)$: It is used to create the electrical contact grids on the surface of the solar cell to collect the generated current.

(N/A) The special technique used for mounting solar cell panels involves installing them on specially designed inclined roofs or structures.
Advantages:
$1$. It ensures that the solar panels are oriented towards the sun,allowing for maximum exposure to sunlight.
$2$. This inclination increases the intensity of solar radiation incident on the panels,thereby enhancing the efficiency of energy conversion.
$3$. It helps in preventing the accumulation of dust,debris,or water on the surface of the panels.

(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 $Natural$ $gas$ $(CNG)$.

(C) Geothermal energy is considered a non-conventional renewable source of energy.
It is derived from the heat stored within the Earth's crust.
Unlike solar or wind energy,which are intermittent,geothermal energy provides a constant and reliable supply of power,allowing it to be harnessed for $24$ hours a day throughout the year.

(N/A) Solar energy manifests itself in the oceans primarily in the following two forms:
$(i)$ Ocean thermal energy: This is due to the temperature difference between the warm surface water and the colder deep water.
$(ii)$ Wave energy: This is caused by the wind blowing across the surface of the ocean,which is ultimately driven by solar heating of the atmosphere.

(B) In an ocean thermal energy conversion $(OTEC)$ plant,the energy is harnessed by utilizing the temperature difference between the warm surface water and the cold water found at depths of up to $2\, km$.
For the efficient operation of such a plant,a minimum temperature difference of $20^{\circ} C$ is required between the surface water and the deep-sea water.

(B) Hot spots are specific regions within the Earth's crust where molten rocks (magma) originating from deeper,hotter layers of the Earth are pushed upward due to high pressure and temperature.
These molten rocks get trapped in these crustal regions,creating localized areas of intense heat.
This geothermal energy can be harnessed for various purposes,such as generating electricity.

(B) source of energy is defined as a system or an arrangement that is capable of providing an adequate and consistent amount of useful energy over a period of time to perform work.