Forests and Wildlife Definitions, Equations and Examples

Forests and Wildlife

Forests are ‘biodiversity hot spots’. One measure of biodiversity of an area is the number of species found there. One of the main aims of conservation is to try and preserve the biodiversity we have inherited as a loss of diversity may lead to a loss of ecological stability.

Stakeholders

When we consider the conservation of forests, we need to Look at the stakeholders who are:

  1. The people who live in or around forests are dependent on forest produce for various aspects of their life.
  2. The Forest Department of the Government which owns the land and controls the resources from forests.
  3. The industrialists from those who use ‘tendu’ leaves to make bidis to the ones with paper mills -who use various forest produce and consider the forest as a source of raw materials for their factories.
  4. The wild life and nature enthusiasts who want to conserve nature in its pristine form.

Forests and Wildlife Definitions, Equations and Examples

Use of Forest Resources

When the Forest Department in independent India took over from the British, local knowledge and local needs continued to be ignored in the management practices. Thus vast tracts of forests have been converted to monocultures of pine, teak or eucalyptus. Such plantations are useful for the industries to ac-cess specific products and are an important source of revenue for the Forest Department.

The case of Khejri Trees: In 1731, Amrita Devi Bishnoi led a group of 363 persons who sacrificed their lives along with her for the protection of khejri trees in khejrali village near Jodhpur. The Government has recently instituted an ‘Amrita Devi Bishnoi National Award for Wildlife Conservation in the memory of Amrita Devi Bishnoi.

The Chipko Andolan: The Chipko Andolan (‘Hug the Trees Movement’) was the result of a grassroot level effort to end the alienation of people from their forests. The movement originated from an incident in a remote village called Reni in Garhwal, high-up in the Himalayas during the early 1970s. The Chipko movement quickly spread across communities and media, and forced the government, to whom the forest belongs, to rethink their priorities in the use of forest produce.

Prejudice against the traditional use of forest areas:

The Great Himalayan National Park contains, within its reserved area, alpine meadows which were grazed by sheep in summer. Nomadic shepherds drove their flock up from the valleys every summer. When this national park was formed, this practice was put to an end. Now it is seen that without the regular grazing by sheep the grass first grows very tall, and then falls over preventing fresh growth.

Management of protected areas, by keeping the local people out by using force cannot possibly be successful in the long run.

Reasons for Damage Caused to Forests

  1. The damage caused to forests cannot be attributed to only the local people.
  2. One cannot turn a blind eye to the deforestation caused by industrial needs or development projects Like building roads or dams.
  3. The damage caused in these reserves by tourists or the arrangements made for their convenience is also to be considered.
  4. We need to accept that human intervention has been very much a part of the forest landscape.

Steps Needed to Preserve our Forests

  1. What has to be managed in the nature and extent of this intervention.
  2. Forest resources ought to be used in a manner that is both environmentally and developmentally sound-in other words, while the environment is preserved, the benefits of the controlled exploitation go to the local people, a process in which decentralized economic growth and ecological conservation go hand in hand.
  3. The kind of economic and social development we want will ultimately determine whether the environment will be conserved or further destroyed.
  4. The environment must not be regarded as a pristine collection of plants and animals. It is a vast and complex entity that offers a range of natural resources for our use.
  5. We need to use these resources with due caution for our economic and social growth and to meet our material aspirations.

Forests and Wildlife Definitions, Equations and Examples

Sustainable Management

The destruction of forests affected not just the availability of forest products, but also the quality of soil and the sources of water. Participation of the local people can indeed lead to the efficient management of forests.

An Example of People’s Participation in the Management of Forests
In 1972, the West Bengal Forest Department recognized its failures in reviving the degraded sal forests in the southwestern districts of the state. The Department changed its strategy, making a beginning in the Arabari forest range of Midnapore district. At the instance of a far-seeing forest officer, A.K. Banerjee, villagers were involved in the protection of 1,272 hectares of badly degraded sal forest. In return for help in protection, villagers were given employment in both silviculture and harvesting operations, 25 percent of the final harvest, and allowed fuelwood and fodder collection on payment of a nominal fee. Soon, these forests of Arabari underwent a remarkable recovery – by 1983, a previously worthless forest was valued Rs 12.5 crores.

Example 1.
We saw in this chapter that there are four main stakeholders when it comes to forests and wildlife. Which among these should have the authority to decide the management of forest produce? Why do you think so?
Answer:
There are four stakeholders when it comes to forests and wildlife: the people who live in or around forests are dependent on forest produce, the Forest Department of the Government which controls the resources from forests, the industrialists who use various forest produce, and, the wild life and nature enthusiasts.

As the local people are directly dependent on the forest, they should be given the authority to decide the management of forest produce as they use traditional methods of exploitation of these resources which ensure that the resources are used in a sustainable manner. Moreover, their existence is directly dependent on these forests and therefore they will not exploit the resources in a manner that could lead to deforestation.

Class 10 Science Notes

Need To Manage Our Resources Definitions, Equations and Examples

Need To Manage Our Resources

We need to manage our resources because the resources of the earth are not unlimited and with the human population increasing at a tremendous rate due to improvement in healthcare. If the natural resources are managed properly, these will last for the generations to come and will not merely be exploited to the hilt for short-term gains.

The proper management of natural resources ensures equitable distribution of resources so that all, and not just a handful of rich and powerful people, benefit from the development of these resources.

The proper management will take into consideration the damage caused to the environment while these resources are either extracted or used. For example, mining causes pollution as large amount of slag is discarded for every tonne of metal extracted.

Need To Manage Our Resources Definitions, Equations and Examples

Example 1.
What would be the advantages of exploiting resources with short-term aims? How would these advantages differ from the advantages of using a long-term perspective in managing our resources?
Answer:
If resources are exploited with short-term aims, it will benefit the present generation and they will be able to utilize the resources for meeting their energy and growth requirements.

However, if long-term perspectives are used in managing our resources, it will benefit the future generations also apart from meeting the requirements of the present generation.

This requires sustainable management of resources and using the resources judiciously by developing technologies for efficient utilization of these resources and avoiding any wastage.

Example 2.
Why do you think there should be equitable distribution of resources? What forces would be working against an equitable distribution of our resources?
Answer:
Equitable distribution of resources is necessary so that people belonging to all classes have access to these resources and are benefitted by utilizing these resources. Equitable distribution of resources will restrict the exploitation, misuse and wastage of these resources by the rich who have access to these resources.

The forces working against an equitable distribution of our resources are:

  1. Access to resources by the rich and powerful
  2. Improper management of resources
  3. Excessive exploitation of resources

Class 10 Science Notes

Ways to Manage Our Resources Definitions, Equations and Examples

Ways to Manage Our Resources

The environment includes our physical surroundings like air, water, soil and all the organisms such as plants, animals, human beings and micro-organisms like bacteria and fungi (called decomposers).

The system of controlling the use of natural resources like forests, wild-life, water, coal and petroleum in such a way as to avoid their wastage and to use them in the most effective way, is called management of natural resources.

Ways to Manage Our Resources Definitions, Equations and Examples

Ganga Action Plan

The pollution of river water is caused by the following factors:

  1. Largely untreated sewage is dumped into the Ganges every day.
  2. Other human activities like bathing, washing of clothes and immersion of ashes or unburnt corpses also cause pollution.
  3. Industries also contribute chemical effluents to the Ganga’s pollution load and the toxicity kills fish in large sections of the river.

This multi-crore project came about in 1985 because the quality of the water in the Ganga was very poor. The contamination of river water can be usually found from two factors:

  1. The presence of coliform bacteria in river water. A coliform is a group of bacteria, found in human intestines, whose presence in water indicates contamination by disease-causing microorganisms.
  2. Measurement of pH of river water: There are some measurable factors which are used to quantify pollution or the quality of the water that we use for various activities and the pH of water is something that can easily be checked using universal indicator.

The Five R’s to Save the Environment

Refuse This means to say No to things that can harm you and the environment.
Reduce This means that you use Less.
Reuse In the reuse strategy, you simply use things again and again.
Recycle This means when a product can nom0l be used for the original purpose. think carefully and use it for some other Useful purpose.
Repurpose This means that you collect plastic, paper, glass and metal items and recycle these materials to make required things instead of synthessing or extracting fresh plastic paper, glass or metal

Ways to Manage Our Resources Definitions, Equations and Examples

Sustainable Development

The concept of sustainable development encourag¬es forms of growth that meet current basic human needs, while preserving the resources for the needs of future generations. It depends upon the willingness of the people to change their perceptions of the so¬cio-economic and environmental conditions around them, and the readiness of each individual to alter their present use of natural resources.

Example 1.

Case Based:
Have you ever visited a town or village after a few years of absence? If so, have you noticed new roads and houses that have come up since you were there last? Where do you think the materials for making these roads and buildings have come from? Try and make a list of the materials and their probable source+s. Discuss the list you have prepared with your classmates. Can you think of ways in which the use of these materials be reduced?
(A) The materials used for road construction are:
(I) Bitumen
(II) Soil
(III) Petrol
(IV) Cement concrete
(a) Both (I) and (II)
(b) Both (II) and (IV)
(c) (II), (III) and (IV)
(d) (I), (II) and (IV)
Answer:
(A) (d) (I), (II) and (IV)

Explanation: A wide variety of materials are used in the construction of roads which are soil (naturally occurring or processed), aggregates (fine aggregates or coarse aggregates obtained from rocks), binders like lime, bituminous materials, and cement, and miscellaneous materials used as admixtures for improved performance of roads under heavy loads and traffic. Soil constitutes the primary material for the foundation, subgrade, or even the pavement (for low-cost roads with low traffic in rural areas)

(B) Which of the following is not used for the construction of buildings?
(a) Coal
(b) Cement
(c) Wood
(d) Steel
Answer:
(a) Coal

Explanation: Building material is any material used for construction purpose such as materials for house building. Wood, cement, aggregates, metals, bricks, concrete, clay are the most common types of building material used in construction.

(C) How is cement used in the construction of buildings and roads obtained?
Answer:
Cement is manufactured by heating a precise mixture of finely ground Limestone, clay and sand in a rotating kiln to temperatures reaching 1450°C.

(D) Assertion (A): Use of cement and petroleum-based materials for road construction should be reduced.
Reason (R): One of the methods to save the environment is to reduce material cost.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(c) (A) is true, but (R) is false.

Explanation: Road and building construction causes lot of environmental pollution as they use cement and other petroleum based products which emit large amount of carbon dioxide in the atmosphere. Large part of the emissions worldwide come from the most ubiquitous part of the human-environment – roads. Cement, used in road construction, contributes 1 ton of CO2 per 1 ton of cement produced. Road Industry is increasingly under pressure to reduce carbon footprint. At the same time, efficiency of industrial processes is at its highest. Reductions of C02 emissions must come from new techniques of asphalt production, often using waste products as alternative input materials. Therefore, in order to save our environment, use of cement and petroleum-based materials for road construction should be reduced.

Class 10 Science Notes

Effect of Our Activities on Environment Definitions, Equations and Examples

Effect of Our Activities on Environment

Since we are an integral part of the environment, our activities also change the environment around us.

Ozone Layer and its Depletion

Ozone (O3) is a deadly poisonous gas that is formed by three atoms of oxygen. It shields the surface of the earth from harmful ultraviolet (UV) rays of the sun, which are known to cause skin cancer in human beings. They also damage the eyes and our immune system.

Formation of Ozone

Ozone is a product of UV radiation acting on oxygen (O2) molecules, which splits apart some molecular oxygen (O2) into free oxygen atoms (O) which combine with the molecular oxygen to form ozone.
Effect of Our Activities on Environment Definitions, Equations and Examples 1

Depletion of Ozone Layer

The amount of ozone in the atmosphere is getting depleted due to the use of synthetic chemicals like chlorofluorocarbons (CFCs), which are used as refrigerants and in fire extinguishers. The CFCs released into the air react with the ozone gas present and destroy it gradually due to which the ozone layer is becoming thinner leading to more UV rays entering the earth.

In 1987, the United Nations Environment Programme succeeded in forging an agreement to freeze CFC production at 1986 levels.

Managing the Garbage We Produce

Effect of Our Activities on Environment Definitions, Equations and Examples

Example 1.
Case Based:
In the first activity, collect waste material from your homes. This could include all the waste generated during a day, like kitchen waste (spoilt food, vegetable peels, used tea leaves, milk packets and empty cartons), waste paper, empty medicine bottles/ strips/bubble packs, old and tom clothes and broken footwear.

Bury this material in a pit in the school garden or if there is no space available, you can collect the material in an old bucket/flower pot and cover with at least 15 cm of soil.

Keep this material moist and observe at 15-days intervals.
In the second activity, use the library or internet to find out more about biodegradable and non- biodegradable substances. These days, new types of plastics which are said to be biodegradable are available. Find out more about such materials and whether they do or do not harm the environment.
(A) When the waste materials collected from home in the first activity was buried in a pit and kept moist and observed at intervals of 15 days, it is observed that:
(I) Kitchen waste like spoilt food, vegetable peels, used tea leaves changed their form the fastest.
(II) Waste paper remained unchanged over a long time.
(III) Empty medicine bottles and strips changed their form and structure but not as fast as kitchen wastes.
(IV) Milk packets and bubble wraps did not change their form or structure during the period of observation.
The correct observations are:
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (I) and (IV)
(d) Both (III) and (IV)
Answer:
(c) Both (I) and (IV)

Explanation: Waste materials such as kitchen wastes (vegetable peels, used tea leaves etc), waste paper, cotton clothes are organic substances and hence are easily degraded naturally, whereas wastes such as empty medicine bottles and strips, bubble wrap, milk packets are made up of glass or plastic and are not degraded naturally.

(B) Given below are names of some waste materials that changed and remain unchanged when buried in the soil.
Plastic box, Rubber tyre, Empty Carton, Vegetable peels, Bubble wrap, Waste paper
What materials are correctly classified as biodegradable and non-biodegradable materials?

Biodegradable Biodegradable
(a) Empty carton, Waste paper, Vegetable peels Bubble wrap, Plastic box, Rubber tyre
(b) Vegetable peels, Bubble wrap, Empty carton Plastic Box, Rubber tyre, Waste paper
(c) Vegetable peels, Rubber tyre, Empty carton Bubble wrap, Waste paper, Plastic Box
(d) Rubber tyre, Empty  carton, Waste paper Vegetable peels, Plastic box

Answer:
(a) Biodegradable: Empty carton, Waste paper, Vegetable peels;
Non-biodegradable: Bubble wrap, Plastic box, Rubber tyre.

Explanation: The substances such as empty carton, waste paper and vegetable peels which are of plant or animal origin are degraded naturally and are said to be biodegradable materials. Whereas, materials such as plastic box, bubble wrap and rubber tyre are non- biodegradable materials.

(C) How long do you think plastic bottles will last in our environment?
Answer:
As plastic is non-biodegradable, it does not get degraded naturally in our environment but persists in our environment for a very long time. Eventually it gets broken down by physical conditions such as heat and pressure. It takes upto 450 years for plastic to be broken down.

(D) These days, new types of plastics which are said to be biodegradable are available. Do such materials cause any harm to the environment?
Answer:
New types of plastics are made from plastics but some chemicals are added to them so that they break down faster when exposed to physical conditions such as air and light. But they also cause harm to the environment as eventually these plastics are broken down into small pieces which persist in our environment and also cause pollution.

(E) Assertion (A): Man-made materials such as glass persist in the environment for a very long time.
Reason (R): Bacteria and other saprophytes break down the organic matter in our environment.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the (A).

Explanation: Man made materials such as plastic and glass persist in our environment for a very long time as they are not degraded naturally by the bacteria and other saprophytes present in our environment which act on organic matter only.

Effect of Our Activities on Environment Definitions, Equations and Examples

Example 2.
How can you help in reducing the problem of waste disposal? Give any two methods.
Answer:
Problem of waste disposal can be reduced by disposing off of garbage in a scientific manner by first segregating them into bior sgradable and non-biodegradable substances. As far as possible, we should use only biodegradable substances such as cloth and paper bags in place of plastic bags.

Improvement in our life styles and changes in our attitudes have led to greater amounts of waste generation, much of which is non-biodegradable. The disposal of waste should be done in a scientific way.

There are various methods of disposing the garbage.

Biodegradable and Non-biodegradable Wastes

All the waste materials produced by the various activities of man and animals can be sub-divided into the following groups:

  1. Biodegradable Wastes
  2. Non-biodegradable Wastes

The waste materials which can be broken down to non-poisonous substances in nature in due course of time by biological processes like the action of micro-organisms are called biodegradable wastes.

Some examples of bio-degradable wastes are cattle dung, compost, animal bones, leather, tea leaves, wool, paper, wheat, wood, hay, cotton, jute, grass, fruit and vegetable peels, leaves, flowers, cake etc. Bio-degradable wastes usually do not pollute the environment.

The waste materials which cannot be broken down into non-poisonous or harmless substances in nature are called non-biodegradable wastes.

Some examples of non-biodegradable wastes are DDT, plastics, polythene bags, synthetic fibres, glass, metal cans, iron nails, silver foils, radioactive wastes etc.

These are the major environmental pollutants as these cannot be decomposed by micro-organisms.

Example 3.
What are the problems caused by the non-biodegradable wastes that we generate?
Answer:
Problems caused by the non-biodegradable wastes that we generate are:

  1. They will persist in our environment for a very long time and hence make the environment harmful and unfit for survival of living organisms.
  2. Their presence will block the flow and transfer of energy, minerals and nutrients in the ecosystem.

Effect of Our Activities on Environment Definitions, Equations and Examples

Example 4.
Give any two ways in which biodegradable substances would affect the environment.
Answer:
The two ways in which biodegradable substances would affect the environment are:

  1. Degradation of these substances by the saprophytes and other microorganisms may release foul-smelling gases thus polluting the environment.
  2. They may become breeding ground for mosquitoes, flies and other pests thus increasing the chances of diseases.

Example 5.
Case Based:
Search the internet or library to find out what hazardous materials have to be dealt with while disposing off electronic items. Find out how these materials affect the environment. Find out how plastics are recycled and whether the recycling process has any impact on the environment.
(A) The hazardous materials to be dealt with while disposing off electronic items are:
(I) cadmium
(II) lead
(III) mercury
(IV) iron
(a) Both (I) and (II)
(b) Both (III) and (IV)
(c) (I), (II) and (III)
(d) (II), (III) and (IV)
Answer:
(c) (I), (II) and (III)

Explanation: Electronic items contain some hazardous materials such as cadmium, lead, mercury, chromium, some compressed gases, PVCs etc. which can contaminate the environment once released by dumping, melting and burning of electronic wastes.

(B) Which of the following is not correct regarding the effect of hazardous materials present in electronic items on the environment?
(a) They can contaminate the groundwater.
(b) They reLease greenhouse gases.
(c) They are highly toxic and carcinogenic.
(d) Burning of these materials lead to depletion of ozone Layer.
Answer:
(b)They release greenhouse gases.

Explanation: Some of the hazardous materials present in electronic items are cadmium, lead and mercury which are toxic and carcinogenic. They can contaminate the groundwater and also enter the food chain through water or soil. Burning of these materials causes depletion of the ozone layer. However, as burning of these materials does not produce carbon dioxide or methane or any other greenhouse gas, it does not cause global warming.

(C) What is the environmental impact of using single-use packaging materials made of plastic?
Answer:
Single use packaging materials made up of plastic are non-biodegradable and hence cause environmental pollution and they persist in the environment for a very long time.

(D) Does the recycLing of plastic cause any damage to the environment?
Answer:
Yes, recycling of plastic causes environmen¬tal damage as burning plastic and other wastes releases dangerous substances such as heavy metals, persistent organic pollutants (POP), and other toxic chemicals into the air and persist as ash waste residues.

(E) Assertion (A): Disposable pLastic cups are preferred over disposable papercups.
Reason (R): Disposable paper cups are biodegradable.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(d) (A) is false, but (R) is true.

Explanation: Disposable paper cups are preferred over disposable plastic cups as paper is biodegradable whereas plastic is non-biodegradable and hence persists in our environment for a very long time.

Class 10 Science Notes

Food Chains and Food Webs Definitions, Equations and Examples

Food Chains and Food Webs

Food or energy can be transferred from one organism to the other by means of food chains. All the food chains begin with the autotrophs as they are the producers of food. Food chain is therefore the sequence of living organisms in a community in which one organism consumes another organism to transfer energy.

Examples of Food Chain

Following are a few examples of food chains:

  1. Grass → Deer → Lion
  2. Grass → Insects Frog → Birds
  3. Plants → Worms → Birds → Cat
  4. Algae → Protozoa Small Fish → Big Fish

Food Chains and Food Webs Definitions, Equations and Examples 1

Example 1.
Which of the following constitute a food-chain?
(a) Grass, wheat and mango
(b) Grass, goat and human
(c) Goat, cow and elephant
(d) Grass, fish and goat
Answer:
(b) Grass, goat and human
Explanation: In a food chain, organism at the higher trophic level feeds on the organism at the Lower trophic level. As goat feeds on grass and humans feed on goats, this is the correct option.

Trophic Levels

The various steps in a food chain at which the transfer of food or energy takes place are called trophic levels. In a food chain, each step forms a trophic level.

  1. The autotrophs or the producers are at the first trophic level. They fix up the solar energy and make it available for heterotrophs or consumers.
  2. The herbivores or the primary consumers come at the second trophic level.
  3. Small carnivores or secondary consumers are at the third trophic level.
  4. Larger carnivores or tertiary consumers form the fourth trophic level.

An example of trophic level: Consider the food chain in a grassland:
Grass → Insects → Frog → Birds
In this food chain, grass represents the 1st trophic Level, insects represent the 2nd trophic level, frog represents the 3rd trophic level and birds are at the 4th trophic level.

The flow of Energy in a Food Chain

  1. The green plants in a terrestrial ecosystem capture about 1% of the energy of sunlight that falls on their leaves and convert it into food energy.
  2. When green plants are eaten by primary consumers, a great deal of energy is lost as heat to the environment, some amount goes into digestion and in doing work and the rest goes towards growth and reproduction.
  3. Ten percent law: An average of 10% of the food eaten is turned into its own body and made available for the next level of consumers. There¬fore, 10% can be taken as the average value for the amount of organic matter that is present at each step and reaches the next level of con¬sumers.
  4. A number of trophic levels are limited: Since so little energy is available for the next level of consumers, food chains generally consist of only three or four steps. The loss of energy at each step is so great that very little usable energy remains after four trophic levels. There are generally, a greater number of individuals at the lower trophic levels of an ecosystem, the greatest number is of the producers.

Food Chains and Food Webs Definitions, Equations and Examples

Example 2.
Will the impact of removing all the organisms in a trophic level be different for different trophic levels? Can the organisms of any trophic level be removed without causing any damage to the ecosystem?
Answer:
Yes, the impact of removing all the organisms in a trophic level be different for different trophic levels. As the largest number of organisms are at the producer level and least number at the highest trophic level in any food chain, removal of organisms at producer level will have an impact on the next higher level as those organ-isms will starve. On the other hand, if organisms belonging to a higher trophic level are removed, the organisms belonging to the lower trophic level will increase greatly in number. This will lead to an ecological imbalance.

No, whenever organisms of any trophic level are removed, it will adversely affect the ecosystem and our environment

Illustration of the 10 percent law: Suppose 1000 joules of light energy emitted by the sun falls on the plants (called producers). We know that the plants convert only one per cent (1%) of the light energy falling on them into chemical energy of food. So, the energy which will be available in plant matter as food will be only 1% of 1000 Joules, which comes to 10 joules. The remaining 1000 – 10 = 990 joules of light energy or solar energy which is not utilized by the plants is reflected back into the environment (see Figure). The ten per cent law will not apply at this stage. It will apply only in the transfer of energy in a food chain.

According to the 10% law, only 10% of 10 jouLes of energy i.e., 1 Joule will be available for transfer to the next trophic level.
Food Chains and Food Webs Definitions, Equations and Examples 2

Food Chains and Food Webs Definitions, Equations and Examples

Food Web

The network of a large number of food chains existing in an ecosystem is called a food web. As the length and complexity of food chains vary greatly and each organism is generally eaten by two or more other kinds of organisms which in turn are eaten by several other organisms. So, instead of a straight line food chain, the relationship can be shown as a series of branching lines called a food web
Food Chains and Food Webs Definitions, Equations and Examples 3

There are six food chains in the above food web, marked as 1, 2, 3, 4, 5 and 6.
1. In the 1st food chain, plants are eaten by rabbit and then rabbit is eaten by hawk:
Plants → Rabbit → Hawk

2. In the 2nd food chain, plants are eaten by mice and the mice are eaten by hawks:
Plants → Mice → Hawk

3. In the 3rd food chain, plants are eaten by mice; mice are eaten by snakes and then snakes are consumed by hawks:
Plants → Mice → Snake → Hawk

4. In the 4th food chain, plants are eaten by seed-eat¬ing birds and the seed-eating birds are consumed by hawks:
Plants → Seed-eating Bird → Hawk

5. In the 5th food chain, plants are eaten up by grasshopper and the grasshopper is consumed by hawks:
Plants → Grasshopper → Hawk

6. In the 6th food chain, plants are eaten by grasshopper, grasshopper is eaten by frog; frog is eaten by snake and then the snake is consumed by hawk:
Plants → Grasshopper →Frog → Snake → Hawk

Energy Flow Diagram

If we study the energy flow diagram in a food chain, we find that the flow of energy is unidirectional. The energy that is captured by the autotrophs does not revert back to the solar input and the energy which passes to the herbivores does not come back to the autotrophs.

Biological Magnification

The increase in concentration of harmful chemical substances like pesticides in the body of living organisms at- each trophic level of a food chain is called biological magnification. These chemicals are absorbed from the soil by the plants and from the water bodies by the aquatic plants and animals. As these are non-biodegradable, they get accumulated progressively at each trophic level. This is also the reason why our food grains such as wheat and rice, vegetables and fruits contain varying amounts of pesticide residue.

Class 10 Science Notes

Ecosystem Definitions, Equations and Examples

Ecosystem

The environment includes our physical surroundings like air, water, soil and all the organisms such as plants, animals, human beings and micro-organisms like bacteria and fungi (called decomposers).

An ecosystem is a self-contained unit of living things and their non-living environment. All the interacting organisms in an area together with the non-living constituents of the environment form an ecosystem. It therefore consists of biotic components and abiotic components.

There are two types of ecosystem:

  1. Terrestrial ecosystem: These are land-based ecosystems such as forest, grassland, desert, mountains etc.
  2. Aquatic ecosystem: These are water based eco-systems such as ponds, lakes, river, sea, aquarium etc.

Ecosystems can also be classified as natural ecosystems and artificial ecosystem. Examples of natural ecosystems are forests, ponds etc whereas examples of the artificial ecosystems are gardens, aquarium and crop- fields.

Components of an Ecosystem

Abiotic Components
The abiotic components of an ecosystem include the physical environment like air, water, soil along with the inorganic substances like carbon dioxide, nitrogen, oxygen, water, phosphorus, sulphur, sodium and other elements present in them. The physical factors which affect our climate such as light, temperature, pressure, humidity are also considered as abiotic components.

Ecosystem Definitions, Equations and Examples

Biotic Components

The biotic component of an ecosystem is a community of organisms which is made up of many inter dependent populations.

It includes three types of organisms:

  1. Producers: These are the autotrophs that synthesize their own food such as green plants and certain blue green algae.
  2. Consumers: These are the heterotrophs that depend on other organisms for food. These organ¬isms consume the food produced either directly from producers or indirectly by feeding on other consumers. They can be further classified as herbivores, carnivores, omnivores and parasites.
  3. Decomposers: These are the organisms that consume the dead remains of other organisms. The microorganisms comprising bacteria and fungi break down the dead remains and waste products of organisms which comprises of complex inorganic substances into simpler inorganic substances that go into the soil and are used up once more by the plants.

The Functioning of an Ecosystem

An ecosystem is a self-sufficient unit. It involves input of energy and matter which are exchanged between the living and non-living components in a cyclic process.

Importance of Decomposers

The decomposers help in decomposing the dead bodies of plants and animals and in this way act as cleansing agents of the environment. The various nutrients which are initially taken by plants from the soil, air and water are returned to the soil, air, and water (nutrient pool) after the death of plants and animals. They help in recycling the materials in the ecosystem.

Ecosystem Definitions, Equations and Examples

Example 1.
What is the role of decomposers in the ecosystem?
Answer:
Decomposers feed on dead and decaying organisms and breakdown the complex organic compounds into simpler substances. In this way, they help in recycling nutrients to the soil and also help in cleaning the environment.

Class 10 Science Notes

Environmental Consequences Definitions, Equations and Examples

Environmental Consequences

The energy source we choose would depend upon on the following factors:

  1. The ease of extracting energy from that source.
  2. The economics of extracting energy from the source.
  3. The efficiency of technology available.
  4. The environmental damage that will be caused by using that energy source.

Example 1.
Hydrogen has been used as a rocket fuel. Would you consider it a cleaner fuel than CNG? Why or why not?
Answer:
Yes, hydrogen can be considered cleaner than CNG as burning of hydrogen produces water, whereas burning of CNG produces carbon dioxide which is a greenhouse gas and hence a pollutant.

Environmental Consequences Definitions, Equations and Examples

Life of Energy Sources

Sources of energy can be classified as renewable and non-renewable sources. Sources that will get depleted some day are said to be exhaustible sources or non¬renewable sources of energy.

Renewable and Non-renewable Sources of Energy

Renewable Source Non-renewable Source
The sources of energy which are likely to be available for a long time and are inexhaustible. For, ex. solar energy, wind energy, ocean waves and biogas. The sources of energy which have taken a very very long time for their formation and cannot be replaced once they are exhausted. For, ex, Fossil fuels like coal, petroleum; and natural gas

Use of Wood as a Fuel

Although wood is a renewable source of energy since trees can be replenished, but a tree usually takes more than 15 years to mature and moreover large scale cutting of trees for obtaining firewood causes environmental problems.

Example 1.
On what basis would you classify energy sources as
(A) renewable and non-renewable?
(B) exhaustible and inexhaustible?
Are the options given in (A) and (B) the same?
Answer:
(A) Renewable sources of energy are the sources which can be replenished over a reasonable period of time naturally, whereas non-renewable sources are those sources of energy which take a very long time for replenishment. Examples of renewable sources are water and solar energy whereas coal and petroleum are non-renewable sources of energy.

(B) Exhaustible sources are the sources of energy which are limited and may get exhausted, whereas inexhaustible sources are those sources of energy that are unlimited and hence may never get exhausted. Examples of exhaustible sources are coal and petroleum whereas water and biomass are examples of inexhaustible sources of energy.

Yes, the options given in (a) and (b) are the same, as they ultimately refer to the same sources of energy

Class 10 Science Notes

Alternative Or Non-Conventional Sources of Energy Definitions, Equations and Examples

Alternative Or Non-Conventional Sources of Energy

We need to exploit new sources of energy and also develop technology to use the known sources of energy more efficiently due to the increasing demand for energy.

Solar Energy

The energy obtained from the sun is called solar energy. Energy is produced in the interior of the sun by fusion reactions taking place between the hydrogen atoms which fuse to form helium and in the process release a tremendous amount of energy.

Solar energy devices: The devices which are used for harnessing solar energy are called solar energy devices. Some common solar energy devices are solar cookers, solar water heaters and solar cell.

Principle of working of solar energy devices: The solar energy received on earth is very small and is approximately 1.4 X (47/100) or 0.66 kJ/s. The solar energy devices should therefore be capable of collecting maximum amount of solar energy and also retain it for its utilization.

There are two types of such devices:

  1. Devices which collect solar energy as heat, for ex, solar heater, solar cooker etc.
  2. Devices which convert solar energy into electricity, for ex, solar cell.

Alternative Or Non-Conventional Sources of Energy Definitions, Equations and Examples

Solar Cookers

Principle: These devices collect solar energy in the form of heat over a period of few hours during a sunny day.
Construction: A solar cooker consists of the following:

Component Purpose
An insulated wooden or metal box painted black from inside The inner walls and bottom of the solar cooker is pointed black to maximize absorption of solar radiations as bLack surfaces absorb much heat. It also helps in reducing heat Losses due to reflection.
Thick glass sheet Glass has o peculiar property that it allows infrared radiations of shorter wavelengths but does not allow infrared radiations of Longer wavelengths to pass through it. This helps the heat to be retained inside the box as the glass cover does not allow the heat to radiate.
Plane mirror reflector It increases the effective area for the collection of the solar energy.

Working: The food to be cooked is placed inside the solar cooker in a metal container. When the sun’s rays fall on the reflector, it sends these rays to the top of the solar cooker. The rays get trapped inside the cooker due to which the temperature inside the box rises to about 100°C to 140°C in a few hours.

Advantages of solar cooker

  1. It saves fuel as it harnesses solar energy
  2. It does not produce any smoke and hence does not cause any pollution.
  3. Since food gets cooked at a relativeLy lower temperatures, the nutrients in the food are preserved.
  4. Their maintenance requires nominal expenditure.

limitations of solar cooker:

  1. It cannot be used for cooking food during night hours.
  2. Even during the daytime, it can be used only on a sunny day and not on a cloudy day.
  3. The direction of the reflector has to be changed continuously so that it always faces the sun.
  4. The box-type solar cooker cannot be used for frying or baking.
  5. There is a high initial expenditure on its installation.

Example 1.
What kind of mirror; concave, convex or plain would be best suited for use in a solar cooker? Why?
Answer:
Since the amount of solar energy available on earth’s surface is not high, the sun’s rays have to be reflected towards the solar cooker. Con-cave mirrors are therefore best suited for use in a solar cooker as they are converging mirrors and converge the sun’s rays towards the focus of the mirror, where the food container is kept. Higher temperatures are achieved in a solar cooker by using concave mirrors as reflectors as compared to plane mirrors.

Solar Cell

Principle: These devices convert solar energy directly into electricity. They are made up of semiconductors like silicon and selenium.

Construction: Solar cells are made of a number of thin layers of silicon containing impurities and are arranged in such a way that when sunlight is incident on them, a potential difference is produced between the two regions of the wafers. A 2 cm2 single solar cell can produce about 0.7 watt of electricity when exposed to sunlight. Solar cells are also known as photovoltaic cells.

Advantages and uses of solar cells:

  1. These are used as the main source of energy in all artificial satellites and space probes.
  2. Solar cells are used as a source of electricity for radio or wireless transmissions and at TV relay stations.
  3. These are used for street lighting and for operating water pumps and radio and television sets in remote areas.
  4. These are used for operating calculators, watches, and toys.

Alternative Or Non-Conventional Sources of Energy Definitions, Equations and Examples

Limitations of solar cells:

  1. The initial cost of installation is quite high.
  2. The availability of special grade silicon used for making solar cells is limited.
  3. The technology to obtain silicon in pure form is expensive.
  4. Since silver is used for connecting the solar cells in a solar panel and silver is quite expensive, it adds to the cost of the solar cell.
  5. The non-availability of efficient systems to store the electricity generated by solar cells and to make it available when required is another problem.

Solar Panel: When a large number of solar cells are connected together by means of connecting wires made of a good conductor like silver, we can obtain a large amount of electricity. This arrangement is known as a solar panel.

Example 2.
Compare and contrast fossil fuels and the Sun as direct sources of energy.
Answer:
Comparison between fossil fuels and sun as direct sources of energy is given below:

Fossil Fuels Sun
1. These are non-renewable sources of energy 1. It is a renewable source is of energy
2. The fossil fuels have limited reserves and are depleting very fast due to overuse 2. Sun is a very large and long-lasting source of energy
3. Use of Fossil fuels results in air pollution. 3. Solar energy is totally clean does not cause any pollution.
4. It is non-expensive 4. These are expensive, though the initial cost is high.
5. These have to be is extracted for use 5. It is readily available, though only during daytime
6. Can be used any time of the day and year 6. Can be used only during daytime when there is plenty of sunshine.

Example 3.
Compare and contrast bio-mass and hydroelectricity as sources of energy.
Answer:
Comparison between bio-mass and hydro-electricity as sources of energy is given below:

Biomass Hydroelectricity
1. Biomass makes use of chemical energy 1. Hydroelectricity makes use of kinetic energy of running or falling water from height
2. usage of biomass for energy requirement causes air pollution 2. Hydroelectricity is pollution-free source of energy
3. Use of biomass does not cause ecological imbalance. 3. Construction of dams for hydroelectricity causes ecological imbalances.
4. Biomass is a relatively more economic source of energy than hydroelectricity. 4. Hydro Electricity is a relatively costly source of energy
5. Residue is used as manure 5. No residue is left behind.

Alternative Or Non-Conventional Sources of Energy Definitions, Equations and Examples

Energy from the Sea

Tidal Energy
The phenomenon of high and low tide give us tidal energy. The energy of the tides or the tidal energy can be harnessed by constructing a dam across a narrow opening to the sea. The water moves in and out of the openings in the dam during high and low tides which rotate the turbines and in this way electricity is generated.

The main limitations of harnessing tidal energy are:

  1. There are a very few sites that are suitable for building dams.
  2. The rise and fall of water during tides is not high enough to generate electricity on a large scale.

Sea Wave Energy

The kinetic energy of huge waves near sea shore is trapped to generate electricity.When winds blow across the surface of the oceans, these get converted into waves which possess a lot of kinetic energy. Wave energy is used for rotation of turbine and production of electricity. Areas with an energy density of 40 MW per km of coastline are considered to be economically viable.

Ocean Thermal Energy (OTE)

The energy available from the ocean due to the difference in temperature between warm surface waters heated by the sun and colder waters found at ocean depths is known as Ocean Thermal energy.

Ocean Thermal Energy Conversion (OTEC) Power Plants: These are devices used to harness the ocean thermal energy. There should be a temperature difference of at least 20°C between surface waters and water at depths up to 2000 m (2 km). The warm surface water is used to boil a liquid like ammonia or CFC which produces vapour which is used to drive turbine of generators. The cold water from the ocean depths is pumped up to convert the vapour again into liquid.
Alternative Or Non-Conventional Sources of Energy Definitions, Equations and Examples 1

Example 4.
What are the limitations of the energy that can be obtained from the oceans?
Answer:
The limitations of energy that can be obtained from the ocean are:

  1. There are very limited locations where dams can be built for harnessing tidal energy-
  2. Wave energy can be trapped for generating electricity only where waves are very strong, which is quite limited.
  3. It is very difficult to efficiently exploit the energy from oceans due to commercial reasons.

Alternative Or Non-Conventional Sources of Energy Definitions, Equations and Examples

Geothermal Energy

The heat from inside the earth can be utilized as a source of energy under certain favorable conditions that are created by natural processes. This energy is known as geothermal energy. The places below the surface of the earth where the hot magma collects are known as hot spots. The underground water in contact with these hot spots get converted into steam which is extracted by drilling holes through which pipes are driven in. The steam which comes up at high pressure is utilized to rotate the turbine of generators.

The advantages of geothermal energy are:

  1. These can be harnessed for 24 hours throughout the year.
  2. It is clean and environmentally friendly.
  3. It is cost effective as the cost of producing electricity is half the cost of producing electricity by conventional means.

Nuclear Energy

Nuclear reactions: The reactions in which the nucleus of an atom undergoes a change forming new atoms and releasing a tremendous amount of energy.

Nuclear fission: When the nucleus of a heavy atom (such as uranium, plutonium or thorium), is bombarded with low-energy neutrons it can be split apart into lighter nuclei.

During a fission reaction, a tremendous amount of energy is released if the mass of the original nucLeus is just a little more than the sum of the masses of the individual products.

Example: The fission of an atom of uranium produces 10 million times the energy produced by the combustion of an atom of carbon from coal.

Nuclear Fusion: The process in which nuclei of low atomic numbers combine to form a heavier atomic nucleus is known as nuclear fusion.

Nuclear Reactor: In a nuclear reactor designedfor electric power generation, such nuclear ‘fuel’ can be part of a self-sustaining fission chain reaction that releases energy at a controlled rate. The released energy can be used to produce steam and further generate electricity.

Nuclear reactors are used for generation of electrical power, production of fissile materials and for nuclear research and are based on nuclear fission.

Nuclear hazards and safety measures:

  1. Nuclear radiation seriously affect human bodies and materials including buildings.
  2. A lot of radioactive materials are produced in nuclear reactors.
  3. It should be ensured that there is no leakage in the moderator or cooling water of nuclear plants which can contaminate water bodies and soil.
  4. The main hazard of nuclear power generation is the storage and disposal of spent or used fuels.
  5. There is a risk of accidental leakage of nuclear radiations.

Class 10 Science Notes

Conventional Sources of Energy Definitions, Equations and Examples

Conventional Sources of Energy

The global demand for energy has increased over the years due to rapid industrialization. It was met largely by the fossil fuels – coal and petroleum. But these are non-renewable and hence will get exhausted if consumed at the present rate. Alternate sources of energy, therefore, need to be explored.

Fossil Fuels

Coal, petroleum and natural gas are known as fossil fuels as they were formed by the fossilized remains of plants of animals. Coal is the fossilized remains of plants while petroleum is the fossilized remains of marine plants and animals. Fossil fuels are classified as non-renewable sources of energy.

Natural Gas

Natural gas is another fossil fuel found with petroleum in oil wells. It contains mainly methane and can be burnt easily to produce heat. When it is subjected to high pressure, it is known as Compressed Natural Gas or CNG. It is an environment-friendly gas as its combustion does not produce any polluting gases or particulate matter. It can also serve as an excellent feed stock for the production of fertilizer and petrochemicals and also as a fuel.

Conventional Sources of Energy Definitions, Equations and Examples

Example 1.
Case-Based:
Take a table tennis ball and make three slits into it. Put semicircular fins cut out of a metal sheet into these slits. Pivot the tennis ball on an axle through its centre with a straight metal wire fixed to a rigid support. Ensure that the tennis ball rotates freely about the axle.

Now connect a cycle dynamo to this. Connect a bulb in series. Direct a jet of water or steam produced in a pressure cooker at the fins as shown in figure below. Note your observations.
Conventional Sources of Energy Definitions, Equations and Examples 1
(A) Select the incorrect observations from the first activity:
The figure in first activity denotes:
(I) the figure denotes a turbine for generating electricity.
(II) the simplest turbines have two moving parts, a rotor-blade assembly.
(III) the moving fluid acts on the blades to spin them and impart energy to the rotor.
(IV) We need to move the fan, the rotor blade, with speed which would turn the shaft of the dynamo and convert the electrical energy into mechanical energy.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (II) and (IV)
Answer:
(d) Both (II) and (IV)

Explanation: The figure denotes a turbine for generating electricity which consists of one moving part, a rotor-blade assembly. The fan, the rotor blade, is moved with speed which would turn the shaft of the dynamo and convert the mechanical energy into electrical energy.

(B) The source of energy which cannot be harnessed efficiently to run the turbine and generat elec¬tricity is:
(a) Fossil fuels
(b) Solar energy
(c) Wind energy
(d) Water
Answer:
(b) Solar energy

Explanation: Fossil fuel coal is used in thermaL power plant to generate electricity whereas water is used in hydro power plants to generate electricity. Wind energy farms are installed for generating electricity from wind mills. Solar energy can be used for generating electricity using solar cells but it cannot run turbine to generate electricity.

(C) What is observed when a jet of water or steam produced in a pressure cooker is directed at the fins in the first activity?
Answer:
When a jet of water or steam produced in a pressure cooker is directed at the fins, the mov¬ing fluid acts on the blades to spin them and impart energy to the rotor.

(D) What is the difference in the way your grand-parents or elders got water for their daily needs when they were young and the present times?
Answer:
Our grandparents and elders used to fetch water from wells or ponds in their village and later using handpumps. In the present time, water is supplied to homes from water treatment plants using pipelines.

(E) Assertion (A): More energy from external sources was spent by our grand¬parents and elders in going to school when they were young as compared to present day students going to school.
Reason (R): School vans and buses use fossil fuels such as petroleum and CNG.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(d) (A) is false, but (R) is true.

Explanation: Our grandparents and elders used to either walk or used bicycle to go to their school and hence they used no external source of energy. Whereas, present day students go to school either by school buses or vans which consume fossil fuels and hence consume more energy from external sources.

Conventional Sources of Energy Definitions, Equations and Examples

Thermal Power Plant

Large amounts offossilfuelare burnt in power stations to heat up water to produce steam which runs the turbine to generate electricity. Thermal power plants are set up near coal or oil fields as it is more efficient to transmit electricity as compared to transport coal or petroleum.

Energy from Water

Water flowing through rivers is an important source of energy which has been utilized for a variety of purposes. The energy of flowing water is a manifestation of solar energy. We are familiar with the energy transformations taking place during the water cycle. The energy of flowing water is used to generate electricity on a large scale at hydroelectric power plants.

Hydroelectric Power Plants

Principle: The kinetic energy of flowing water is transformed into potential energy by constructing high rise dams on rivers. The stored water is made to fall on turbine blades which rotate the armature of the electric generators to produce electricity.

Advantages and Uses of Hydroelectricity

  1. It does not cause any pollution.
  2. It uses water which is a renewable source of energy.

Limitations of Hydroelectric Power Plants

  1. These can be constructed only at a Limited number of places.
  2. When dams are built on rivers, large land areas get submerged which causes environmental and social problems.
  3. It destroys the natural habitat of plants and animals and even human habitations.
  4. It can adversely affect the ecosystem of adjoining as well as areas downstream.
  5. It decreases fertility of soil in downstream areas.
  6. It creates the problem of satisfactory rehabilitation of displaced people.

Improvements in the Technology for Using Conventional Sources of Energy Biomass

Biomass is a form in which solar energy manifests itself. Plants and animals and excreta of living organisms and their bodies contribute to the biomass. It also includes wastes from tree, wood, cow dung, charcoal and baggage (residue of sugarcane after extracting itsjuice).

  1. Biogas is an excellent fuel as it contains up to 75% methane.
  2. Charcoal burns without flames and is relatively smokeless
  3. It does not leave any residue like ash in wood, charcoal and coal burning.
  4. It has a high heating capacity.

Biomass as fuel: Wood is used as a source of heat. Firewood is burnt in traditional chulhas for cooking and heating water.

Conventional Sources of Energy Definitions, Equations and Examples

Comparison between traditional chulhas and smokeless chulhas:

Traditional Chuthas Smokeless Chuthas
1. Incomplete burning of firewood produces smoke. 1. Complete combustion of firewood takes place which produces no smoke.
2. These are inefficient as only 8-10% energy of the fuel gets used. 2. These ore highly effcient.
3. These need more fuel. 3. These need Less fuel
4. These are not attached with chimneys. 4. These are attached with chimneys.

Charcoal

Charcoal is another commonly used fuel that is obtained from wood. When wood is burnt in a Limited supply of oxygen, water and volatile materials present in it get removed and the charcoal is left behind as a residue. This process of burning wood in a limited supply of oxygen is called destructive distillation of wood. Charcoal is an expensive fuel as destructive distillation of one kilogram of wood yields only 0.25 kg charcoal.

Advantages of Charcoal over Wood

  1. Charcoal burns easily, producing no smoke.
  2. It gives twice as much heat as is obtained by burning same mass of wood. These qualities make charcoal a better fuel than wood.

Biogas Plants

In a biogas plant, degradation of biomass is carried out by anaerobic micro-organisms called anaerobic bacteria in the presence of water but in the absence of oxygen. The components of a biogas plants are:

Mixing Tank: Equal amounts of animal dung and water are mixed in this tank. This mixture is called slurry which is then fed to the digester tank.

Digester tank: The anaerobic micro-organisms break down the complex compounds of the biomass in this underground tank. The digesters are designed like a sealed chamber. This process takes about 50-60 days during which gases like methane, carbon dioxide, hydrogen and hydrogen suLphide are produced.

Outlet for gas: As more and more biogas is formed, it is taken out through the outlet pipe.

Overflow tank: When more and more biogas is formed inside the digester, it exerts pressure on the slurry in the digester tank which forces the spent slurry to the overflow tank.

Conventional Sources of Energy Definitions, Equations and Examples

Advantages of biogas plants

  1. The main constituent of biogas is methane, which is an excellent fuel and burns without producing smoke.
  2. Burning of biogas does not leave any residue.
  3. Biogas can be used for heating, lighting and for producing electricity.
  4. The slurry which is left behind is an excellent manure as it is rich in nitrogenous and phosphorus compounds.
  5. It gives us a safe method to dispose off wastes.

Wind Energy

Moving air is called wind. Sun’s energy is responsible for the movement of air from one region to another thus constituting wind. Wind possesses kinetic energy as it is moving air. Some of the common applications of wind energy are in winnowing and windmills.

Windmills

Principle: Windmills are devices which convert wind energy into mechanical or electrical energy and can therefore be used for working water lifting pumps, flour mills and electric generators.

Construction: It consists of a structure similar to a Large electric fan that is erected at some height on a rigid support. The blades of a windmill are designed to create a pressure difference between its different regions when wind strikes them. This pressure difference creates a turning effect due to which the blades rotate with a speed which depends upon the wind velocity.

Wind energy farm: When a large number of windmills are erected over a large area and the energy output of each windmill is coupled together to generate electricity on a commercial scale, this is known as a wind energy farm. The wind power potential of our country is about 20,000 MW. The largest wind energy farm near Kanyakumari in Tamil Nadu can generate 380 MW of electricity.

Advantages of windmills:

  1. It uses wind energy which a renewable source of energy.
  2. Its use does not cause any environmental pollution.
  3. It requires no recurring expenses for the production of electricity.

Conventional Sources of Energy Definitions, Equations and Examples

Limitations of windmill:

  1. Windmills can be established only at those places where wind blows for most part of the year.
  2. The wind should be strong and steady to maintain desired levels of production. The minimum wind velocity required for a functional windmill is about 15 km/h.
  3. Large areas of land are required to establish wind energy farms. An area of about 2 hectares is required for a 1 MW generator.
  4. The setting up of wind energy farms is quite costly.
  5. There should be some back-up facilities to take care of the energy needs during a period when there is no wind.
  6. They need a high level of maintenance as the tower and blades are exposed to rain, sun storm and cyclone etc.

Example 2.
How has the traditional use of wind and water energy been modified for our convenience?
Answer:
Wind and water energy have been used tra-ditionally for our energy requirements. But, the traditional use of wind and water energy have been modified to generate electricity on a large scale by installing wind energy farms and dams.

Class 10 Science Notes

Good Sources of Energy Definitions, Equations and Examples

Good Sources of Energy

Energy comes in different forms and one form can be converted to another. Energy, in the usable form, is dissipated to the surroundings in less usable forms. Hence, any source of energy we use, to do work, is consumed and cannot be used again.

Characteristics of Good Fuel

  1. It should have a high calorific value, i.e., it should release a large amount of heat on burning.
  2. It should not produce a lot of smoke.
  3. It should be readily available.

Characteristics of a Source of Energy

  1. It should do a large amount of work per unit volume or mass.
  2. It must be convenient to use.
  3. It should be easy to transport and store.
  4. It should be capable of delivering a desired quantity of energy at a steady rate over a long period of time.
  5. Be economical

Good Sources of Energy Definitions, Equations and Examples

Example 1.
Case-Based:
List four forms of energy that you use from the morning, when you wake up, till you reach school. Identify the sources of these different forms of energy.
Let us find out the various options we have when we choose a fuel for cooking our food and the criteria one would consider when trying to categorize something like a good fuel.
(A) The different forms of energy that we use in our daily life in urban homes are:
Select the row containing the incorrect option:

Form of energy Source
(a) Electrical energy Water or coal
(b) Muscular energy Food
(c) Heat energy Fossil fuels
(d) Mechanical energy Wood

Answer:
(d) Form of Energy: Mechanical energy; Source: Wood

Explanation: Mechanical energy is used in our daily life in cycling, mixer etc. The source may be electrical or chemical energy, but not wood, as wood is not considered a good source of energy.

(B) Given below are statements regarding choosing a fuel for cooking our food. Select the incorrect statements.
(I) Kerosene should be used as a cooking fuel as it is readily available.
(II) LPG or Natural Gas should not be used for cooking as they emit a lot of smoke.
(III) Biogas should be used as a cooking fuel in rural areas since it is a renewable source of energy.
(IV) Coal should not be used as a cooking fuel since it is produces a lot of smoke on burning.
(a) Both (I) and (II)
(b) Both (II) and (III)
(c) Both (III) and (IV)
(d) Both (I) and (IV)
Answer:
(a) Both (I) and (II)

Explanation: Though kerosene is readily avail-able, it should not be used as a cooking fuel as it emits harmful pollutants. Liquefied Petroleum Gas (LPG) or Natural Gas should be used for cooking as they do not emit any smoke when burnt.

(C) Write two criteria one would consider when trying to categorise something as a good fuel.
Answer:

  1. Amount of heat produced on burning fuel
  2. Ease of availability

(D) How would the choice of fuel for cooking be different if you lived in a forest and in New Delhi?
Answer:
Some of the factors deciding the choice of fuel are the ease of availability, transportation, storage and cost. If a person lived in a forest, he would mainly use firewood as fuel, since it is readily available. However, for a person living in a city like New Delhi, he would use LPG or Natural gas (piped natural gas) as a fuel for cooking since it is readily available and produces no smoke.

(E) Assertion (A): Different fuels are used for cooking and heating room in winter.
Reason (R): Calorific value of fuels is the only criteria for selecting a fuel.
(a) Both (A) and (R) are true and (R) is the correct explanation of the assertion.
(b) Both (A) and (R) are true, but (R) is not the correct explanation of the assertion.
(c) (A) is true, but (R) is false.
(d) (A) is false, but (R) is true.
Answer:
(c) (A) is true, but (R) is false.

Explanation: The choice of fuels depends on several factors such as calorific value of fuels, availability, cost, ease of storage and transport, emission of smoke etc.

Good Sources of Energy Definitions, Equations and Examples

Example 2.
If you could use any source of energy for heating your food, which one would you use and why?
Answer:
Fuel that heats the food faster without destroying the nutritional value of the food would be preferred for heating food. So, an electric oven or a heater would be better.

Class 10 Science Notes

Electric Generator Definitions, Equations and Examples

Electric Generator

An electric generator works on the principle of electromagnetic induction. When an armature is rotated in a magnetic field, an electric current is induced in the coil. Here, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity which is based on the phenomenon of electromagnetic induction.

Components of Electric Generator

Armature: It contains coiLs of wire of many turns.
Rings: These are of two types:- Solid ring, used in A.C. generator and split ring, used in D.C. generator.

When a solid ring is used, as the coil rotates, the direction of induced currents in both the segments change, i.e., the polarity of the current changes in the respective arms after every half a rotation.

When a split-ring is used, one brush is at all times in contact with the wire moving up in the field due to which unidirectional or direct current is produced.
Electric Generator Definitions, Equations and Examples 1
Split-ring commutator for a DC generator

The difference between Direct current and Alternating Current Direct current is unidirectional, that is, it always flows in one direction. The alternating current reverses its direction periodically. Power can be transmitted over long distances using AC without much loss of energy.

Electric Generator Definitions, Equations and Examples

Example 1.
Explain different ways to induce current in a coil.
Answer:
Different ways to induce current in a coil are:

  1. Relative motion between a coil and a magnet either by moving a coil near a stationary magnet or moving a magnet near a stationary coil.
  2. By changing the current flowing through a coil.

Example 2.
Choose the correct option.
A rectangular coil of copper wire is rotated in a magnetic field. The direction of the induced current changes once in each
(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution
Answer:
(c) half revolution

Explanation: The direction of motion of coil changes after every half revolution thereby changing the direction of induced current also.

Class 10 Science Notes