XI Computer Model Question

 

XI Biology Model Questions

 

XI Chemistry Model Questions

 

XI Physics Model Question

Sample Project Report

A PROJECT REPORT ON STUDY BOILING POINT OF WATER

 

 

 

 

 

By:

Abc Efg

Grade:………Section:

Roll No:……..

 

Submitted to:

[Teacher’s Name]

Department of Science

…………………………. School

…………………………

2021

Introduction:

Kinetic theory states that all molecules in matter are in constant motion (Kane and Sternheim, 1984). As these molecules absorb more energy they have a higher amount of random movement. As energy is absorbed in the form of heat the average kinetic energy (temperature) of the molecules will increase except during a phase change. The absorbed energy used in the phase change breaks the attractive forces between the molecules, thus transformation occurs in the orientation of the molecules. An example of a phase change would be the boiling point of water which is a change from a liquid to a gas. This can be observed by using a temperature versus time line graph when the slope becomes zero (plateau) The boiling point of water is expected to be 100.00 _oC (Merck, 1976).

 

Objective:

The purpose of this experiment is to determine the boiling point of water.

 

Hypothesis:

If the pressure in the classroom is close to 1 atmosphere, then the boiling point of water should be approximately 100 degrees Celsius.

 

Materials List:

500 ml beaker distilled water, thermometer, hot plate,

Word Processing Software

 

Procedure:

The required materials were selected and taken to the workstation. The beaker was filled with approximately 300 ml of distilled water. The beaker was gently placed on the hotplate.

The thermometer was placed in the beaker and the initial temperature was recorded. The hotplate was switched on to high.

The temperature was recorded every 2 minutes until 6 minutes after boiling began.

The hotplate was turned off and the materials were allowed to cool for at least 10 minutes before the equipment was dismantled.

 

Figure 1. The equipment for this experiment was set up as shown in this figure.

Data / Results / Observations:

Quantitative Results

Table 1 Graph displaying data obtained from the heating of water from 0 to 16 minutes

Figure 2. A line graph of temperature versus time of the data obtained in Table 1

Qualitative Results

Numerous small bubbles formed at the bottom of the beaker at 70.6 _oC. The size and rate of bubble formation increased as the temperature increased. At 100.0 _oC the rate and size of bubble formation remained constant. At that temperature, there was constant production of steam.

 

Calcuations / Analysis:

 

Conclusion:

It was determined from the data plotted in the temperature versus time graph (Figure 2) that the boiling point of water is 99.51 oC. This concurs very closely with the stated hypothesis, therefore the experiment was deemed a success. The percent error was found to be 0.49%. Possible sources of error could have involved impurities in the water and human error in reading the thermometer. Possible sources of error may be impurities in the water which may be chemicals from dirty glassware. Improvements would include more accurate thermometers, clean equipment and proper reading of the thermometer.

 

 

References:

Kane, Joseph W. and Morton M. Sternheim. Physics. New York: John Wiley & Sons, 1984 ed.

Merck, Josef. Merck Index of Chemical Constants. New York: Benjamin/Cummings Publishing Company Inc. 1976.

Project Report Instruction

 Science Project Report Format

General Information:

·       12 pt Times New Roman font / Fair handwriting

·       Double Spaced

·       1 inch margins

·       Always write in third person

·       Write in Full Sentences except for the materials list

·     Each student should submit at least a project report on a subject. 

Important Reminders for a Project Report 

Ø  Check Spelling

Ø  Use Significant figures and units regarding measurements and calculations Avoid personal pronouns

Ø  Headings should stand out and each section should be separated by 1 line Neatness counts -> use rulers when needed (especially when using tables and

Ø  graphs), type if possible

Ø  Do not copy verbatim (word for word) from the lab handout or any other source. This is plagiarism and would result in a zero mark and possible further consequences.

Title Page - Heading, Name, Class Name, Teacher Name, Date Lab Report

Introductory Paragraph – This section should be written in complete sentences and should connect lab concepts to class content, The introduction should provide background information on the history of the concepts tested, scientists, theories, and any laws tested in the experiment. Cite Sources Used. The introduction should contain any prior knowledge on which the experiment is based including an explanation of principles, definitions, experimental techniques, theories, and laws.

 

State Problem / Purpose The objective is a concise statement in complete sentences outlining the purpose of the experiment. The purpose section of a lab is where you tell the reader your reason for doing the lab in the first place and briefly summarize any relevant background information about the experiment, including any relevant chemical equations and/or algebraic equations.

Hypothesis: (When your project quantitative: based on data) Possible if_then_ statement. Define any variables such as manipulated, measured, controlled and the cause and effect predicted. The hypothesis is a one-line sentence where you discuss how you’ll solve the problem at hand. The statement after “if” is the independent variable. The independent variable is whatever you will do to solve the problem. The statement after “then” is the dependent variable, because what happens will depend on what you did in the first place. Generally, the dependent variable will be the problem you mentioned in the purpose.

Materials: (Bulleted List) The materials section is a list of all equipment, reagents (chemicals), and computer programs that were used to complete the experiment.

Drawings of the apparatus setup should be included in this section if needed. The materials list must be complete. Indicate how much of each material will be used in the experiment.

If you plan on arranging some of the equipment into a more complex setup (for example, if you are going to heat something over a Bunsen burner, you will need a ring stand, wire gauze, etc.), draw it as well as mention the equipment used.

Procedure: This section may be written in either paragraphs or numbered steps. Explain the test design, and allow for pictures and diagrams. The procedure is a detailed statement (step by step) of how the experiment was performed such that the experiment could be repeated using your report. Safety precautions that were followed should be stated in this section. The procedure must be written in the impersonal (3rd person) past tense:

e.g. We are taking the temperature every 2 minutes. NO

The temperature was taken every 2 minutes. YES

 

Data / Results / Observations: This is a collection of observations, measurements, multiple trials, data tables, charts, and repeating steps. This section may consist of quantitative and/or qualitative observations of the experiment. A qualitative piece of data is a written description and/or sketch of what was seen during the experiment.

Quantitative information may be in the form of a table or simply a written description. When graphs are required, special attention should be paid to the following items: the type of graph expected (straight line or curve), utilizing the entire graph paper, plotted point size, title of the graph, and axis labels. When numerous measurements have occurred, data is to be placed in a data table whenever possible. Figure headings are placed below the figure and should give a short description of the figure. The figure number should be in bold print. Table headings are found above the table and should also have a brief description.

 

Analysis / Calculations: Graphs, Error Calculations, Equations, Statistical Analysis - One example of each type of calculation should be included. Results from numerous calculations should be placed in a data table with the proper number of significant figures and correct units. % yield and % error calculations should be included when possible.

Conclusion: The conclusion is a concise statement that answers the objective. The result of percent error and/or percent yield should be discussed and compared with known results. A portion of the conclusion should be dedicated to error analysis which discusses any possible sources of error that may have contributed to the percent error or yield. The conclusion should be written in the impersonal past tense. How to change the experiment for improved results, What did you learn? Explain what the results are telling you, Accept/Reject the Hypothesis, Answer any questions posed by the lab or teacher. A one-line sentence that supports the hypothesis or states that the hypothesis is incorrect.

For example, if you proved the hypothesis that “If I poke myself in the eye, then my eye will hurt”, this first sentence would be “When I poked myself in the eye, it hurt.”

If the hypothesis didn’t work, an explanation of what possibly went wrong. These should be specific suggestions (I should have heated the mixture to 55⁰ C), not general suggestions (I should have heated it more). List at least two possible errors in the lab, as well as ways to prevent those errors in the future. The errors you mention should be errors that you can do something about, not mystical errors that probably did not occur.

 

Reference: Any information borrowed from another source that is not common knowledge must be cited within the text of the report. The sources should be alphabetical in order.

e.g

Harihar Paudyal, Manoj Kumar Thapa,Arjun Kumar Gautam,Bhesha Raj Adhikari,Parashu Ram Paudel. Principles of Physics Grade XI. Ayam Publication, 2077.

 

 (https://en.wikipedia.org/wiki/Boiling_point)

 

Additional Notes:

Reports will be graded largely on their ability to clearly communicate results and important conclusions to the reader. You must, of course, use proper English and spelling, along with comprehensible logic and appropriate style. You should proofread your report as well as spell-check it.

-Neatness and organization will also influence the grade a report receives. Be sure to follow explicitly the format indicated above.

- be concise.

-Avoid qualitative phrases such as "the results were quite close" or "heat fluxes were in good agreement with the correlation." Be as quantitative as possible.

- Do not copy material without citing the source. This includes lab manuals, text books, your neighbor, old labs, etc. Plagiarism, of any degree, will not be accepted.

Biology Project Work

 List of Biology Project Works:

1.       Collect the sample of cryptogams (Algae, Bryophytes, Pteridophytes) and study their

characteristics.

1.       Observe and compare the morphological adaptation of hydrophytes, xerophytes and

xerophytes.

2.       Prepare a report on local varieties and improved varieties of crops and vegetables in your

area.

3.       Visit the forest or vegetation types in your nearby area and prepare a report on it.

4.       Prepare a report on the role of botanical garden in conservation of plants in Nepal

5.       Survey any locality regarding any topics related to theory course of Biology (visit to

zoological museum/zoo/protected areas/natural habits- forest/lake or river) and writing a

report of it

6.       Prepare a report on causes and consequences of environmental pollution in your locality.

7.       Observe different cultivation methods of Mushroom and prepare a report on it.

8.       Look for resources like library, journals, web surfing, field observations etc and study

present status and scope of Biotechnology in Nepal.

9.        Prepare a report on the topic "significances of the biology and biology education with

different sectors i.e. industrial development, medicine, bio-technology, agriculture etc".

10.   Prepare a report on "recent development of genetic field and their implications in human

life"

11.   Prepare model of DNA and RNA

12.   Visit the human beings and observe the dominant and recessive characteristics of human

beings and prepare a report on it

13.   Measure the blood pressure (BP) of human bodies and predict the trends of age wise BP.

14.   Visit the poultry farming or fish farming in local area and prepare a report by including

the place, farming method, marketing etc.

15.   Conduct the survey on common communicable diseases prevailing in local area. Prepare

a report by including the disease, causes, preventing measures.

16.   Prepare a report on trends, causes and consequences of migration in local level.

17.   Prepare functional models of different system of human body.

Chemistry Project Work

 List of Chemistry Project Works:

1.       Observe in your surroundings (kitchen, school, shop, etc.) and make a possible list of organic and inorganic compounds. How are they different? Why is it necessary to study them separately, put your argument?

2.        Study of the methods of purification of water.

3.       Testing the hardness of drinking water from different sources and the study of cause of

hardness.

4.       Study of the acidity of different samples of the tea leaves.

5.       Preparation of molecular models using stick and clay.

6.       Study of adulteration of food materials.

7.       Study of application and adverse effects of pesticides on human health.

8.       Study of use and adverse effects of plastics on environment.

9.       Analysis of soil samples. (elaboration need pH, humus content)

10.   Investigation on corrosion and rusting on iron.

11.   Comparison of ground and surface water quality of a given place-colour, odour, pH,

conductivity, turbidity etc.

12.   Design and development of water filter (Charcoal filter with sand can be designed and

water quality can be monitored).

13.   Observe brick industry/chemical industry/old smooky cooking kitchen/use of

chemical fertilizers/use of insecticides/ vehicular smokes, etc. and draw the

conclusion of environmental impact of the chemical pollution.

14.   Visit nearby paper industry if possible or consult e-media and observe the raw

materials required, steps of manufacturing and quality endorsement of paper. Also,

prepare a complete report.

15.   Visit nearby cement industry if possible or consult e-media and observe the raw

materials required, steps of manufacturing and quality endorsement of cement. Also,

prepare a complete report.

16.   Collect different brands of OPC and PPC cement and observe their setting duration.

17.   Collect different types of plastics (or synthetic polymers) and study the effect of heat

on them.

18.   Extraction of essential oils from selected plants using Clevenger’s apparatus.

19.   Preparation of soap using coconut oil or any vegetable oil.

20.   Study of quantity of casein present in different samples of milk.

21.   Study of formation of rust in the iron nail in various conditions.

22.   Study of the different types of food preservatives used in different food available in

the market.

23.   Study of common food adulterants in fat, oil, butter, sugar, turmeric powder, chilli

powder and pepper.

24.   Investigation on the foaming capacity of different washing soaps and the effect of

addition of sodium carbonate on them.

25.   Study the acidic nature of alcohol and phenol.

26.   Study the distinction between aliphatic aldehyde, aromatic aldehyde and aliphatic

ketone.

27.   Detect the presence of acetic acid in vinegar.

28.   Study the nitrous acid test of primary, secondary and tertiary amines.

29.   Study the different types of dyes.

30.   Study the positive and negative effect of drugs.

31.   Study the setting of cement.

32.   Study the presence of pesticides residues in fruits and vegetables.

33.   Test of protein in various foods.

Physics Project Work

 1. Study the variation in the range of a jet of water with angle of projection

2. Study the factors affecting the rate of loss of heat of a liquid

3. Study the nature and size of the image formed by a convex lens using a candle and a

screen.

4. Study of uses of alternative energy sources in Nepal

5. Study of energy consumption patterns in the neighborhood.

6. Study of study of electricity consumption pattern in the neighborhood.

7. Study of application of laws and principle of physics in any indigenous technology.

8. Verification of the laws of solid friction.

9. Study the temperature dependence of refractive index of different liquids using a hollow

prism and laser beam.

10. Study the frequency dependence of refractive index of glass using a glass prism and

white light beam.

11. Construct a hygrometer using dry and wet bulb thermometers and use it to measure

relative humidity of a given place.

12. Design and construct a system to demonstrate the phenomenon of total internal

reflection (TIR) of a laser beam through a jet of water.

13. Construct a digital Newton meter using the concept of potential divider.

14. Study the traffic noise level in your town using a sound pressure level (SPL) meter.

15. Design and construct a step-up transformer.

16. Construct a simple device to measure angle of contact of a liquid with a solid surface and also calculate the surface free energy of some hydrophobic and hydrophilic surfaces.

17. Calculate the surface free energy of some hydrophobic and hydrophilic surfaces.

18. Construct a simple DC motor using a disk type magnet and a battery.

19. Construct a model of AC generator/dynamo.

20. Construct a current balance to measure magnetic flux density of a U-shaped magnet.

21. Construction of a step down transformer attached with a full wave rectifier made from semiconductor diodes.

22. Construct a thermocouple thermometer and use it to investigate how temperature of a Bunsen burner flame changes with the height of the flame from the top of the burner.

23. Study of the status of hydroelectricity in Nepal.

24. Study of application of laws and principle of physics in any indigenous technology.

25. Verify Joule’ law.

26. Investigation on Peltier effect.

27. History of space exploration

28. Study on history of nuclear power in Asia

Fluid Dynamics

Energy

 

Nuclear Energy and Other Source of Energy

Energy

Energy has taken the place of basic need in our daily life. One way or another everything depends on upon energy. The source of energy is the one which can provide an adequate amount of energy in a convenient form over a long period of time.

Thus, we can say that energy required in every field. Usually, energy in the form of fuel and electricity is used to carry out all the activities whether in houses, offices or industries. All sources of energy can be divided into two main categories: renewable sources of energy and non-renewable sources of energy.

Renewable Sources of Energy

The sources of energy which are inexhaustible and are being continuously supplied by nature are known as renewables sources of energy.

For examplei) Wind ii) Flowing water iii) Ocean tidal energy iv) Interior of the earth v) Biogas Renewable Sources of Energy vi) The sun vii) Plants and vegetables

Non-renewable Sources of Energy

The sources of energy which are exhaustible and have been formed in nature long ago are known as non-renewable sources of energy.

Example: i) Coal ii) petroleum iii) fissionable materials like uranium iv) Natural0gas

These sources of energy are also known as conventional sources of energy.

Importance of Energy

Importance of energy in our everyday life are as follows:

1. we need the energy to develop a personality,
2. to sustain life energy is needed,
3. to cook food and performing daily activities like sitting, talking, walking, thinking etc,
4. to do different mechanical work life lifting a load, driving automobiles, carrying things from one place to another place etc.

Energy Crisis

The continuous use of a non-renewable source of energy causes the serious problem of energy scarcity. Such an energy scarcity is known as an energy crisis. Due to the overgrowth of modern civilisation1 and ever increasing population more energy has been used up. For example, the petroleum products, coal etc are being finished, forests are being reduced and the ground level has decreased. Overuse of non-renewable source of energy has brought this scarcity.

Conservation of Energy

In order to solve energy crises, we have to reduce the use of excess energy which is called conservation of energy. The following steps are to be taken to conserve the energy.

1. The renewable is created in sources of energy should be used in place of non-renewable one.
2. The use of firewood should be reduced as far as possible.
3. Deforestation should be stopped and forestation should be implemented.
4. Solar and electrical vehicles should be used in place of petroleum vehicles.
5. The world’s population must be controlled.
6. Awareness about the importance of energy conservation should people.

Transformation of energy

The process of changing or converting one form of energy into another form is known as transformation energy.

Some of the examples of transformation of energy are:

1. When we listen to music then electrical energy is converted into sound energy. In the case of watching TV, electrical energy is converted into sound energy and light energy.
2. When an electric current passes through an electric bulb, it glows and gives out light and heat. Electrical energy is converted into heat and light energy.
3. When we rub our hand, they become warm. In this case, mechanical energy is converted into heat energy.
4. When a pendulum swings, the potential energy is converted into kinetic energy and vice-versa.

Nuclear Energy

The energy released during a nuclear reaction is called nuclear energy. Nuclear energy can be obtained from two types of reaction: nuclear fission and nuclear fusion.

Nuclear fission

The process in which the heavy nucleus of a radioactive atom splits up into smaller nuclei when bombarded low energy neutrons is called nuclear fission. A tremendous amount of energy is released from nuclear fission which is converted into electric energy.

When uranium 235 atoms are bombarded with slow neutrons, the heavy uranium nucleus breaks up to produce two medium weight atoms, barium -139 and krypton-94, with emission of 3 neutrons.

₉₂U²³⁵+₀n¹→₅₆Ba¹³⁹+₃₆Kr⁹⁴+₀n¹+Tremendous amount of energy

₉₂U²³⁵+₀n¹→₅₆Ba¹³⁹+₃₆Kr⁹⁴+₀n¹+Tremendous amount of energy

Nuclear Fusion

The process in which two nuclei of light elements combine to form a heavy nucleus, is called nuclear fusion.The nuclear reactions which occur at extremely high temperature are called thermonuclear energy.

When deuterium atoms are heated to an extremely high temperature under extremely high pressure, then two deuterium nuclei combine together to form the heavy nucleus of helium, and a neutron is emitted.

₁H²+₁H²→₂He³+₀n¹+Tremendous amount of energy

₁H²+₁H²→₂He³+₀n¹+Tremendous amount of energy

Thermal Power Plant

A thermal power plant produces electricity by burning coal or oil.

Working of a Thermal Power Plant

Coal or oil is burnt in a furnace to produce heat energy. This heat energy is used to boil water in order to produce steam. The steam produced in the water reservoir is allowed to fall in the turbine rotates it with high pressure. The steam falling on the turbine rotates it with high speed. A generator or dynamo connected with the turbine through an axis rotates with high speed and produce electricity. The electricity so produce is transmitted to a distant place through transmission wires.

Hydroelectric Power Plant

The electricity produced by the flowing water is known as hydro-electric power.

For the construction of hydro-electric power plant, a dam or water reservoir is made over a river. The energy stored in a dam which has potential energy is allowed to fall on the water wheel or turbine. Flowing water with potential energy makes turbine rotate with an axle and the armature of the generator. The armature of the generator between two poles of a strong magnet. The rotation of the armature of the generator rotates within two poles of a strong magnet. The rotation of the armature of the generator between two poles of a strong magnet gives rise to electric current or electricity. This electricity is transmitted to the sub-stations through a transformer for further distribution to the houses factories.

Principle of Generation of Hydroelectricity

The potential energy of water stored in a dam is converted into kinetic energy of the falling water. The water falls on the turbine, so kinetic energy of the flowing water is converted into kinetic energy of the armature of the generator connected to the turbine. Then kinetic energy is converted into electrical energy known as hydroelectricity.

 

Advantage

1. It does not cause any environmental pollution.
2. Hydroelectricity is a cheap and renewable source of energy.
3. The hydroelectric power plant can be set up anywhere at a suitable place.

Disadvantage

1. Hydroelectric power is generated only near the rivers having water throughout the year. The electric power has to be carried to the sub-stations for distribution to the house and factories situated far off from the sites of hydroelectric power stations. This is done through the transmission wires, so a lot of money has to spend on this process.
2. A large area of fertile land submerged at the site of the dam constructed for tapping energy from the flowing water.
3. A large number of people residing near the site of a dam are dislocated. So, a lot of problems are to be faced in rehabilitating.
4. Large ecosystems are destroyed when land is submerged under the water reservoir of a dam.

Applications of Hydroelectricity

1. Hydroelectricity can be used in transportation.
2. It can be used for various household purposes such as cooling, heating, lighting etc.
3. It can be used to irrigate agriculture land.
4. Hydroelectricity can be used in industries to operate various machines.

Wind Energy

The wind possesses kinetic energy. The kinetic energy of the wind is known as wind energy.

Uses of Wind Energy

The kinetic energy of the wind can be used to

1. move the sail boats in lakes, rivers and seas.
2. operate water pumps to draw underground water.
3. run the flour mills to grind the grains.
4. produce electricity.

A device used to convert wind energy into the mechanical energy of the machine is called windmill.

Construction

It consists of a wheel rotates about an axle mounted on a pole. The wind energy is used to rotate the wheel about its axis.

Uses

1. The windmill to operate a water pump
2. The windmill for producing electricity

Windmill to operate a water pump

The axle of the windmill is connected to a crank rod. The free end of the water pump rod or piston is connected to U-bend of the crank rod.

Working: When the wind strikes the blades of the windmill, the kinetic energy of the wind is used to rotate the wheel of the windmill. As a result, the axle or shaft attached to the wheel rotates which turns the crank rod. The u-bend of the crank rod produces up and down motion of the piston of the water pump. Hence, the underground water is drawn to the surface of the earth.

Windmill for producing electricity (wind generator)

When the armature of a generator rotates between two poles of the strong magnet, then electricity is produced. Windmill rotates when the wind falls on the wheel of a windmill. So the armature of the generators rotates between two poles of a magnet along with the rotation of the wheel of the wind. Electric current is produced. This is how, the kinetic energy of the wind is converted into electric energy.

Advantages

1. Wind energy produces no smoke and no harmful gases.
2. Wind energy is free and running it is also very economical.
3. The source of wind energy is unlimited.

Bio-mass energy

During photosynthesis process, solar energy is converted into chemical energy. So, plants have stored chemical energy in the forms of biomass. The matter contained in the body of different plants and animal have biomass. The gas obtained from biomass is called biogas.

Advantages

1. It is a renewable source of energy.
2. It’s production is very economical.

Disadvantage

1. Due to the release of smoke, it causes air pollution.
2. A large amount of energy cannot be produced by biomass.

Application

1. The biomass energy can be used in the home for heating and cooling purposes.
2. It can be used for heating food in food industries.
3. The biogas like gobar gas can be used for lightening purposes.

Gobar gas or Bio Gas

Biogas is a mixture of various gases formed when the animal dung is mixed with water and ferment in the absence of air.

Biogas Plant

The arrangement of producing biogas from animal dung, human excreta, industrial and domestic wastes is known as biogas plant. The arrangement of producing biogas from animal dung, human excreta, industrial and domestic wastes is known as biogas plant. A biogas plant consists of a well shaped, underground tank T called digester, which is made of bricks, and has a dome-shaped roof D. The digester is a kind of sealed tank in which there is no oxygen which acts as a gas-holder for the biogas. On the left side of the digester tank is sloping inlet chamber I and on the right side is a rectangular outlet chamber O, both made of bricks. The inlet chamber is for introducing fresh dung slurry into the main digester tank whereas outlet chamber is for taking out the spent dung slurry after the extraction of biogas. The inlet chamber is connected to a mixing tank M while outlet chamber is connected to the overflow of tank F. There is a gas out let S at the top of the dome having a value V.

Working

Cow-dung and water are mixed in equal proportions in the mixing tank M to prepare the slurry. This slurry of dung and water is fed into the digester tank T through the inlet chamber I. the digester tank is filled with dung slurry up to cylindrical level, the dome being left free for the collection of biogas. It might take 50 to 60 days for the new-gas plant to become operative. Gradually when the biogas starts collecting in the dome, it exerts pressure on the slurry in the digester tank and forces the spent slurry to go into overflow tank F, through the outlet chamber O. the spent slurry is gradually removed by the overflow of the tank. The spent dung slurry left after the extraction of biogas is rich in iron and phosphorous compounds and forms good manure.

Advantages

1. Biogas is used for cooking food and heating water.
2. Biogas does not produce smoke during and hence there is no air pollution.
3. It is the cheapest source of energy.

Solar Energy

The energy emitted by the sun in the form of heat and light is known as solar energy. The hot air rises up and the cold air from the surrounding rushes to occupy its space. This is how the air moves. Moving air possesses kinetic energy which is also termed as the wind.

Sunlight makes photosynthesis possible through which plants prepare their food. The solar energy evaporates the water oceans, lakes and ponds. The evaporated water forms cloud. These clouds on cooling give rain. The rainwater is collected in the reservoir having potential energy. Finally, potential energy is converted into kinetic energy by letting water flow in higher speed. Kinetic energy rotates the turbine which is connected with the huge magnet. Current is induced by the magnet.

Even the energy of fossil fuels like coal, petroleum and natural gas also comes from solar energy. Due to high pressure, the biomass of dead animals and plants are converted into the fossil fuels like coal petroleum and natural gases.

The sun contains mainly light elements like hydrogen and helium. When the atoms of these elements fuse together at an extremely high temperature in the interior of the sun, a large amount of energy is radiated in the form of heat.

Solar Constant

The solar constant is defined as the energy received from the sun in one second by the unit square meter area of the outer edge of earth’s atmosphere exposed perpendicularly to the radiation of the sun at average distance between the earth and the sun. The upper part of the earth receives solar energy equal to 1.4-kilo joule per second per square meter (1.4 kJ/s m²). The amount is known as solar constant.

Thus, solar constant = 1.4 kJ/s m² or 1.4 kW/m²

Application of Solar Energy

1. It is used by green plants during photosynthesis.
2. The solar energy powers the flow of wind.
3. The solar energy causes rainfall by evaporating water on the earth’s surface.
4. It is used to produce electricity from the solar cells.
5. It is used for drying clothes and food grains.
6. It is used for transportation.
7. The solar energy sustains all lives on the earth.
8. It is used for heating water using the solar heater and various other purposes.

Solar Devices

The devices which convert solar energy into other forms of energy are called solar devices. Examples: solar cooker, solar furnace, solar water heater etc.

Solar Cookers

Construction:

It consists of a wooden box in which a metallic box painted black is fitted. The space between the wooden box and the metallic box is filled with an insulating material which minimizes the heat loss by conduction and radiance. The metallic box is covered by a thick glass sheet. A plane mirror is used to reflect the sun rays into the box shown in the figure. The uncooked food placed in the black container is put inside the box.

Working:

The plane mirror reflector is adjusted in such a way that maximum sunlight falls on it. The light reflected by the plane mirror falls on the thick glass sheet cover. The heat radiation coming from the sun and have a short wavelength and high energy pass through the glass sheet and is absorbed by the black container or any other object placed in the box and black surface of the box. The temperature inside the box is between 100 ^oC to 140 ^o C.

Advantages

1. The cost of cooking food in the solar cooker is very small as money is only spent upon solar cooker.
2. It can cook two or three dishes at a time.
3. It saves the costly fuel like wood, gas, kerosene oil etc.
4. Nutrition value of the food is preserved as there is no burning of fuel.
5. It can cook multiple dishes at a time.

Solar Heater

In a solar heater, plane reflector the solar radiation is reflected into a blank pipe containing water. If the solar radiation falls on the plane reflector, on the black pipe it reflects the solar radiation. The black pipe absorbs the heat and uses it for heating water in it.

 

Solar Furnance

It consists of a large number of movable plane mirrors and a parabolic reflecting surface. The parallel beam of light falling on the parabolic mirror is focused at a small area, F

Application

A solar furnace is used in melting metals of high melting point.

Solar cell

A device which converts sunlight into electrical energy is known as a solar cell.

Construction

The solar cell consists of an array of semiconductor device called diode. When solar energy falls on such a diode, a small potential difference is created across it. When the large numbers of diodes are connected in series, a large potential difference can be obtained. As the large numbers of series of diodes are connected in parallel, a large current can be obtained. Each diode is called solar cell and an array of such cells is called a solar battery or solar panel. For example, to run a water pump by the solar battery, the external battery is connected to run an electric motor.

Advantages

The main advantages of solar cells are

1. Solar cells have no moving parts, they require almost no maintenance, and work quite satisfactorily without the use of any light focusing device.
2. They can be set up in remote, inaccessible and very sparsely inhabited area where power transmission is difficult.

Uses of Solar Cells

1. They are used to operate electric bulbs and tubes in the remote villages and area.
2. They are used to supply electricity in artificial satellites.
3. They are used for operating traffic lights.
4. They are used in running light vehicles like tempo, cars, microbuses etc.
5. They are used in street lighting.

Fuel Energy

The material which produces energy while burning is called fuels. Petrol, wood, kerosene, diesel, etc are the examples of fuel.

Applications of Fuels

1. Fuels are used for generating electricity.
2. Fuels are used in transportation.
3. Fuels are used for cooking, lightening and heating process.
4. Fuels are used in industries for various purposes.
5. Fuels like petrol and diesel are used in running various grinding mills.

Geothermal Energy

The earth has three layers i.e., the core, the mantle and the crust. The core is the central part of the earth surrounded by the mantle. The outermost part of the earth which surrounds mantle is the crust. The mantle of the earth has molten mass called magma. This magma consists of molten rocks, gases and steam at very high temperature. Due to some geological changes, the hot magma rises up and is collected in the crust of the earth. The regions in the crust where the hot magma is collected are called hot spots. The heat energy stored in the hot spots of the earth’s crust is called geothermal energy.

Advantages

1. Geothermal energy causes no pollution, so it is environmentally friendly.
2. Geothermal energy can be converted continuously into electricity throughout the air.
3. The cost of converting geothermal energy into electricity is very less.

Tidal Energy

The rise and fall of the ocean due to the attraction of the moon is called tide. The rise in water is called high tide and fall in water is called low tide. The kinetic energy of water during tides is used to produce electricity.

Tides power plants are constructed near Bays. Tides rising water is allowed to fall on the turbine of the generator which produces electricity. Thus, the kinetic energy of the water is converted into electrical energy.

During low tides, gates of the dam are closed and hence the water level behind the dam rises. The raised water has potential energy. Again gates are opened and the water is allowed to fall back into the bay. This falling water is used to rotate the turbine of the generator. Hence, the electricity is produced.

Global Energy Consumption Pattern and Demands

The amount of energy consumed by a country depends on the living standards of its citizens and the degree of its industrialization. The average energy required for a man to maintain his daily activities require about 20 k cal per day. At present, the global energy consumption per capita per day is about 2000 times the 20 K calorie he needs for maintaining life. The figure shows the global energy consumption from 1900 to 1990.

At present, about 40% of demand for energy in the world is obtained from oils. Similarly, about 20% of the total energy consumption provided by coal, about 20% by natural gas, wool 10%, nuclear resources 7% and hydroelectric power 3%. Remaining required energy is fulfilled by the resources like solar energy, tidal energy, wind energy etc.

 

Energy Use in Nepal

In Nepal, existing energy sources are classified into two major groups:

1. Conventional Energy Sources
2. Alternative Energy Sources

Nepal is not an industrially developed country. So that biomass energy as the burning of wood, agricultural waste products, and animal waste are the important resources of energy. About 94% of the total energy consumption of the country is met from biomass, out of which 80% is met by burning wool and 8.5% from animal waste.

Pollution

Pollution is the addition of something in the ecosystem, which has a detrimental effect on the environment. Odum (1971) defined pollutants as an undesirable change in the physical-chemical and biological activities. Air containing dust, smoke and CO₂ makes air polluted. Likewise, the high concentration of chemical fertilizer such as nitrogen, phosphorous and potassium in the soil pollutes the land.

Types of pollution

Air pollution

An undesirable change in the physical, chemical or biological characteristics of air is called pollution. The substances which pollute the air called pollutants.

Sources of air Pollution

1. The major industrial exhausts which contain carbon monoxide, sulphur dioxide, an oxide of nitrogen, chlorine, fluorine etc.
2. Burning solid fuels such as firewood, agricultural wastes, coal etc are the causes of air pollution.
3. Chlorofluoro Carbon (CFC) and ammonia released by the refrigerators etc.
4. Different biocides such as pesticides, insecticides, fungicides etc.
5. Tobacco smoke.
6. Electric power plants, burning fossils fuels etc.

Control of Air Pollution

1. Control over the kinds of fuel used in cars, aeroplanes, power stations, etc.
2. The establishment of more smokeless zones.
3. Disposal of wastes by dilution processes.
4. The government should encourage scientific societies and newspapers to create awareness among people about pollution and environment.
5. The garbage in big cities should be treated with cobalt rays.

Effects of Air pollution

1. Air pollution causes respiratory tract infection (RTI) and asthma.
2. It deteriorates the cultural heritage and trees.
3. It brings various skin and eye allergy.
4. It is the main causes of global warming

Water pollution

Degradation in the quality of water is called water pollution. Water covers over the 3/4th part of the earth’s surface. It is a very important resource for people and the environment. Water pollution affects drinking water, rivers, lakes and oceans all over the world. In many developing countries, it is usually a leading cause of death, by people drinking from polluted water sources. Drainage and wastage from industries, laboratory, hospitals, and homes are the main factors that cause water pollution.

Causes of water pollution

There are various causes of water pollution. Main causes of water pollution are described below:

1. A mixture of the drain in water: In urban areas drainage and drinking water pipe are brought through the same route. If drainage pipe gets burst then drinking water pipe gets contaminated with drain water which pollutes the water.
2. Washing and cleaning near water resources: In rural areas, many people shares common tap where they wash their clothes and bath nearby water resources which pollute water.
3. Mixing of fertilizers in water: Farmers use different fertilizers on their farm which are carried to river by rainfall. Fertilizers get mixed with the river.
4. Wastage from different sectors: Wastage produced by hospitals, industries, and houses are thrown in the river. Due to lack of garbage disposal water gets polluted.
5. Mismanagement of drain: Drains are directly thrown into the water in urban areas. Sometimes people directly throw wastage in water.

 

 

Control of Water Pollution

1. Renovating the existing sewer lines and connecting them to the central sewer line by branch and trunk lines.
2. All domestic sewage be centrally collected.
3. Industries may be forced to treat the effluents to a requisite quality standard and to be connected to the main sewer line.
4. Wastes from other sources like cattle fields and livestock farming should be managed properly.
5. All municipal and industrial waste water should be centrally collected and managed.

Effects of water pollution

1. Water pollution causes water-borne disease like diarrhoea, dysentery, and cholera.
2. It also brings various skin allergies if taken the bath with polluted water.
3. Acid rain deteriorates cultural heritages.
4. It has the negative impact on plants.
5. Aquatic animals cannot survive in polluted water.

Global Warming

In the atmosphere greenhouse effect is mainly due to the carbon dioxide layer. In the upper atmosphere, there is a protective layer of ozone. This ozone layer does not allow the ultraviolet radiation to enter into the earth’s atmosphere. Lower atmosphere contains carbon dioxide which traps the infrared radiation from different sources and maintains a suitable temperature. If there is an excess of carbon dioxide in the atmosphere, the temperature of the earth increases which is called global warming.

Acid rain

When the various gases like CO₂, SO₂, NO₂, combine with rainwater then their respective acids will be produced. These acids will react on the ground along with rain water in the cocktail form. This process is called acid rain. In the atmosphere, these gases react with water vapour and formed their corresponding acids like H₂CO3, H₂SO4, and others. When rainfall occurs these acids get mixed with rain and forms acid rain.

Effect of acid rain

1. The acidity of the soil increases which causes the reduction of productivity of the soil.
2. The acidity of water bodies increases which cause the decline in the population of aquatic organism.

 

 

Green House Effect

The artificial house which is made by glass or plastic inside which the temperature will be more than the outer environmental temperature is called greenhouse. The artificial greenhouse provides controlled environment for plants.

Examples of Green House Effect

1. The interior of a car parked in the sunshine with its window becomes very hot due to the greenhouse effect.
2. Rooms of a house in cold countries whose windows are closed and sunlight fall on then become warm due to the greenhouse.
3. Solar cookers and solar furnace are heated due to the greenhouse effect.

Advantages of artificial greenhouse

1. It provides the controlled environment for plants inside it. The plants which can be found in the desert can be grown in the Himalayan region inside it.
2. Those plants which are obtained in summer can be planted in winter inside it.

The Atmosphere of the Earth is Natural Green House

The water vapours and carbon dioxide in the atmosphere are good observers of infra-red radiation of longer wavelengths than that of the infra-red radiations of shorter wavelengths. The solar radiation passes easily through the atmosphere. The heat radiations passing through the atmosphere are observed by the earth’s surface and various objects like plants, water and rocks. The temperature of the earth increases. The earth’s atmosphere emits infrared radiation of longer wavelengths. These infrared radiations of longer wavelengths are absorbed by water vapours and carbon dioxide in the atmosphere. Due to this heat radiation, the warming of the earth’s atmosphere takes place.