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Class 10th Science Chapter 15 – Our Environment and Sustainable Management | Introduction and Importance

Our Environment and Sustainable Management

Introduction and Importance

Class 10 CBSE Science | Foundation | Competitive Preparation

🌍 Our Environment and Sustainable Management | Introduction and Importance

1. Introduction to Environment

Environment means the total surroundings in which organisms live and interact. It includes both living (biotic) and non-living (abiotic) components.

Biotic components: Plants, animals, microorganisms, human beings and other living organisms.

Abiotic components: Air, water, soil, sunlight, temperature, minerals, humidity and other non-living factors.

🌳

Environment = Biotic + Abiotic Components

🌱 Plants
Producers

↔

🐄 Animals
Consumers

↔

🦠 Microorganisms
Decomposers

↔

☀️ Air • Water • Soil
Abiotic Factors

Hindi: पर्यावरण उन सभी जैविक और अजैविक घटकों का समुच्चय है जो किसी जीव के जीवन, वृद्धि, विकास और अस्तित्व को प्रभावित करते हैं।

2. What is an Ecosystem?

An ecosystem is a functional unit of nature in which living organisms interact with one another and with the physical environment.

Examples of ecosystems include:

• Forest ecosystem
• Pond ecosystem
• Grassland ecosystem
• Desert ecosystem
• Marine ecosystem
• Crop-field ecosystem

Ecosystem = Biotic Components + Abiotic Components + Their Interactions

Exam Point: An ecosystem is not simply a collection of organisms. It also includes interactions among organisms and between organisms and their physical surroundings.

3. Why is the Environment Important?

The environment provides the basic conditions and resources necessary for life.

Environmental Resource	Importance
Air	Required for respiration and photosynthesis; atmospheric gases also regulate climate.
Water	Essential for cellular processes, drinking, agriculture and ecosystems.
Soil	Supports plant growth and provides minerals and habitat for organisms.
Sunlight	Main energy source for most ecosystems and drives photosynthesis.
Plants	Produce food and oxygen and provide habitats and resources.
Animals	Participate in food chains, pollination, seed dispersal and nutrient cycling.
Microorganisms	Decompose organic matter and help recycle nutrients.

4. Human Dependence on Environment

Humans depend on the environment for food, water, oxygen, energy, raw materials, medicines, shelter and many economic activities.

Agriculture depends on soil, water, sunlight and suitable climatic conditions. Industries depend on natural resources such as minerals, water and energy sources.

Important: Human development and environmental protection are closely connected. Excessive exploitation of natural resources can disturb ecological balance.

5. Environmental Balance

An ecosystem maintains a dynamic balance through interactions among organisms and physical factors. Food chains, food webs, decomposition and nutrient cycling are important parts of this balance.

Natural Balance

☀️ Solar Energy

→

🌱 Producers

→

🐇 Consumers

→

🦠 Decomposers

Nutrients are returned to the environment through decomposition and can be reused by producers.

6. Environmental Problems

Human activities can create environmental pressures. Major problems include:

• Air pollution
• Water pollution
• Soil pollution
• Deforestation
• Loss of biodiversity
• Climate change
• Excessive waste generation
• Resource depletion
• Habitat destruction
• Plastic pollution

Pollution is the undesirable change in the physical, chemical or biological characteristics of the environment that can adversely affect organisms and ecosystems.

7. What is Sustainable Management?

Sustainable management means using natural resources and managing human activities in a way that meets present needs while maintaining the ability of ecosystems and resources to support future generations.

Hindi: सतत प्रबंधन का अर्थ प्राकृतिक संसाधनों का इस प्रकार विवेकपूर्ण उपयोग और प्रबंधन करना है कि वर्तमान आवश्यकताएँ पूरी हों तथा भविष्य की पीढ़ियों की आवश्यकताओं को पूरा करने की क्षमता बनी रहे।

Sustainable Development = Present Needs + Resource Conservation + Future Needs

8. Sustainable Development

Sustainable development seeks to balance environmental protection, economic development and social well-being.

Dimension	Meaning
Environmental	Protect ecosystems, biodiversity, air, water, soil and natural resources.
Economic	Support livelihoods and development while avoiding unnecessary resource depletion.
Social	Promote human well-being, equity, health, education and access to resources.

9. The Three Pillars of Sustainability

🌿
Environment
Ecological Protection

💰
Economy
Responsible Development

👨‍👩‍👧‍👦
Society
Human Well-being

Sustainability requires consideration of all three dimensions together.

10. Sustainable Use of Natural Resources

Natural resources should be used efficiently and responsibly.

Resource	Sustainable Practice
Water	Rainwater harvesting, efficient irrigation, prevention of water pollution and reuse where appropriate.
Forests	Afforestation, reforestation, controlled use and protection of biodiversity.
Energy	Energy efficiency, conservation and increased use of suitable renewable sources.
Soil	Prevent erosion, maintain fertility and use appropriate agricultural practices.
Minerals	Efficient use, recycling and recovery of materials.
Wildlife	Habitat protection and conservation of biodiversity.

11. Reduce, Reuse and Recycle

Reduce: Use fewer resources and generate less waste.

Reuse: Use an item again instead of discarding it after one use.

Recycle: Process waste materials to make useful materials or products.

Reduce → Reuse → Recycle → Recover → Responsible Disposal

12. Importance of Waste Management

Improper disposal of waste can contaminate soil and water, create unpleasant surroundings, harm wildlife and contribute to disease transmission and pollution.

Good waste management includes segregation, reduction, reuse, recycling, composting where suitable and safe disposal of residual waste.

13. Biodiversity and Sustainability

Biodiversity refers to the variety of life, including diversity within species, between species and of ecosystems.

Biodiversity contributes to ecosystem functioning, food resources, pollination, nutrient cycling, genetic resources and resilience.

Key Point: Conservation of biodiversity is an important part of sustainable environmental management.

14. Intergenerational Equity

Intergenerational equity means considering the needs and rights of future generations while making decisions about resource use today.

For example, excessive extraction of groundwater today may reduce water availability for future communities. Sustainable management attempts to avoid such long-term problems.

15. Carrying Capacity

Carrying capacity refers broadly to the maximum level of population or activity that an environment can support over time without unacceptable degradation of its resources and ecological functions.

In real ecosystems, carrying capacity is not always a fixed number. It can change with resource availability, environmental conditions and human activities.

16. Renewable and Non-Renewable Resources

Renewable Resources	Non-Renewable Resources
Can be replenished naturally on a relatively short human timescale when managed properly.	Exist in finite quantities or are replenished extremely slowly on human timescales.
Solar, wind and sustainably managed biomass are examples.	Coal, petroleum and natural gas are examples.
Still require responsible management and can have environmental impacts.	Overuse leads to depletion and many may produce pollution when extracted or used.

17. Environmental Conservation

Environmental conservation means protecting, maintaining and wisely managing natural ecosystems, species and resources.

• Protect forests and wildlife.
• Reduce pollution.
• Conserve water.
• Use energy efficiently.
• Reduce unnecessary consumption.
• Promote recycling.
• Protect soil.
• Maintain biodiversity.
• Use renewable resources responsibly.

18. Sustainable Management in Daily Life

Daily Activity	Sustainable Choice
Electricity	Switch off unused appliances and use energy-efficient devices.
Water	Repair leaks and avoid unnecessary wastage.
Transport	Walk, cycle, use public transport or share rides where practical.
Shopping	Prefer durable products and avoid unnecessary single-use items.
Waste	Segregate waste and recycle suitable materials.
Food	Avoid unnecessary food waste and use resources efficiently.

19. Important Environmental Terms

Term	Meaning
Environment	Total living and non-living surroundings of organisms.
Ecosystem	Functional unit formed by organisms and their physical environment interacting together.
Ecology	Study of interactions among organisms and between organisms and their environment.
Natural Resource	Material or feature of nature that is useful to humans or other organisms.
Conservation	Protection and wise management of natural resources and biodiversity.
Sustainability	Ability to maintain ecological, social and economic systems over the long term.
Pollution	Undesirable environmental change caused by pollutants or harmful activities.
Biodiversity	Variety of living organisms at different levels of biological organisation.

20. Important CBSE Concept: Development vs Sustainable Development

Development may improve infrastructure, production, income and services. However, development that causes severe environmental degradation may create long-term costs.

Sustainable development attempts to achieve development while conserving natural resources and maintaining environmental quality for the future.

21. 30 MCQs with Answers

1. Environment includes:

A. Only living organisms

B. Only non-living components

C. Both living and non-living components

D. Only plants

Answer: C
Environment consists of both biotic and abiotic components.

2. Which is an abiotic component?

A. Temperature

B. Bacteria

C. Grass

D. Deer

Answer: A

3. Which is a biotic component?

A. Water

B. Soil

C. Sunlight

D. Fungi

Answer: D

4. An ecosystem consists of:

A. Only animals

B. Biotic and abiotic components and their interactions

C. Only plants

D. Only microorganisms

Answer: B

5. Which is the major energy source for most ecosystems?

A. Sun

B. Soil

C. Wind

D. Minerals

Answer: A

6. Sustainable management primarily aims to:

A. Maximise waste

B. Stop all development

C. Use resources responsibly for present and future needs

D. Increase resource depletion

Answer: C

7. Which practice conserves water?

A. Leaving taps running

B. Repairing leaking pipes

C. Over-irrigation

D. Dumping waste into rivers

Answer: B

8. The three broad dimensions of sustainability include:

A. Environment, economy and society

B. Soil, rocks and minerals

C. Plants, animals and fungi

D. Air, water and sunlight

Answer: A

9. Which action follows the principle of reuse?

A. Throwing a bottle away after one use

B. Burning all waste

C. Buying unnecessary products

D. Using a durable container repeatedly

Answer: D

10. Which is a non-renewable resource?

A. Solar energy

B. Wind

C. Coal

D. Tidal energy

Answer: C

11. Biodiversity refers to:

A. Only plant diversity

B. Variety of life

C. Only animal diversity

D. Only ecosystem size

Answer: B

12. Which is NOT generally a sustainable practice?

A. Recycling

B. Rainwater harvesting

C. Efficient energy use

D. Uncontrolled deforestation

Answer: D

13. Intergenerational equity means:

A. Ignoring future needs

B. Giving all resources to one generation

C. Considering future generations in present decisions

D. Stopping all resource use

Answer: C

14. Which organism is mainly responsible for decomposition?

A. Bacteria and fungi

B. Deer

C. Tiger

D. Grasshopper

Answer: A

15. Which of the following can contribute to soil pollution?

A. Responsible composting

B. Proper recycling

C. Uncontrolled dumping of hazardous waste

D. Afforestation

Answer: C

16. The best meaning of conservation is:

A. Unlimited exploitation

B. Protection and wise management

C. Complete abandonment of resources

D. Increasing pollution

Answer: B

17. Which is an example of renewable energy?

A. Coal

B. Petroleum

C. Natural gas

D. Solar energy

Answer: D

18. Which action follows “Reduce”?

A. Avoiding unnecessary consumption

B. Buying extra plastic items

C. Throwing reusable products away

D. Increasing wastage

Answer: A

19. Soil is important because it:

A. Has no role in ecosystems

B. Supports plants and stores nutrients

C. Produces sunlight

D. Replaces air

Answer: B

20. Which activity helps protect biodiversity?

A. Habitat destruction

B. Illegal hunting

C. Habitat conservation

D. Uncontrolled pollution

Answer: C

21. Sustainable management is important because resources are:

A. Always unlimited

B. Not always unlimited and ecosystems have limits

C. Completely unnecessary

D. Always replaceable immediately

Answer: B

22. Which practice can reduce solid waste?

A. Reuse of materials

B. Increasing single-use products

C. Dumping waste in water

D. Burning all waste

Answer: A

23. Sustainable development attempts to balance:

A. Only industrial growth

B. Only environmental protection

C. Development and environmental/social considerations

D. Only resource extraction

Answer: C

24. Which is an example of conservation of energy?

A. Keeping lights on unnecessarily

B. Using energy-efficient appliances

C. Increasing electricity wastage

D. Leaving fans running in empty rooms

Answer: B

25. Which component is directly involved in photosynthesis?

A. Sunlight

B. Plastic

C. Glass

D. Metal

Answer: A

26. Which is a major cause of biodiversity loss?

A. Habitat destruction

B. Conservation

C. Reforestation

D. Protected areas

Answer: A

27. Which statement about renewable resources is correct?

A. They are always impact-free

B. They can never be depleted

C. They require no management

D. Their sustainable use still requires responsible management

Answer: D

28. Which one is an example of responsible waste management?

A. Segregation of waste

B. Dumping waste in rivers

C. Burning plastics openly

D. Throwing all waste together

Answer: A

29. The term “carrying capacity” is associated with:

A. Unlimited growth

B. The ability of an environment to support a population/activity over time

C. Only industrial production

D. Only soil fertility

Answer: B

30. The most appropriate goal of sustainable management is:

A. Maximum consumption

B. Maximum waste production

C. Responsible long-term use and conservation of resources

D. Complete removal of human activity

Answer: C

22. 30 Subjective Questions with Answers

2 Marks 1. Define environment.

Environment is the total of living and non-living surroundings of organisms and the interactions among them.

2 Marks 2. What are biotic and abiotic components?

Biotic components are living organisms such as plants, animals and microorganisms. Abiotic components are non-living factors such as air, water, soil, light and temperature.

2 Marks 3. What is an ecosystem?

An ecosystem is a functional unit in which organisms interact with each other and with the physical environment.

2 Marks 4. Define sustainable management.

It is the responsible management and use of resources so that present needs are met while ecological systems and future needs are protected.

2 Marks 5. What is biodiversity?

Biodiversity is the variety of living organisms at different levels, including genes, species and ecosystems.

2 Marks 6. Give two examples of renewable resources.

Solar energy and wind energy.

3 Marks 7. Explain three reasons why the environment is important.

The environment provides air and water, supplies food and raw materials, and supports ecosystems and biodiversity.

3 Marks 8. Explain Reduce, Reuse and Recycle.

Reduce means lowering consumption and waste. Reuse means using products again. Recycle means processing waste materials into useful materials/products.

3 Marks 9. Why is conservation of biodiversity important?

Biodiversity supports ecosystem functions, provides useful biological resources and increases ecological resilience. Its loss can disturb food webs and ecosystem processes.

3 Marks 10. State three ways to conserve water.

Repair leaks, use efficient irrigation/water-use practices and collect rainwater where suitable.

3 Marks 11. What is intergenerational equity?

It means considering the needs of future generations while using resources today, so that present consumption does not unnecessarily reduce future opportunities.

3 Marks 12. Give three examples of environmental problems.

Air pollution, deforestation and biodiversity loss. Other examples include water pollution, soil pollution and climate change.

4 Marks 13. Differentiate between renewable and non-renewable resources.

Renewable resources can be replenished naturally on relatively short timescales when properly managed, e.g. solar and wind energy. Non-renewable resources are finite or replenished extremely slowly, e.g. coal and petroleum.

4 Marks 14. Explain the three pillars of sustainability.

The three broad pillars are environmental protection, economic well-being and social well-being. Sustainable decisions consider these dimensions together rather than focusing on only one.

4 Marks 15. Explain the importance of waste management.

Waste management reduces pollution, prevents contamination of soil and water, protects wildlife and promotes recovery/recycling of useful materials. Proper segregation and safe disposal are important.

4 Marks 16. Explain how humans depend on the environment.

Humans depend on the environment for food, water, oxygen, energy, raw materials, medicines and ecosystem services. Agriculture, industries and settlements also depend on natural resources.

5 Marks 17. Explain sustainable development with examples.

Sustainable development aims to meet present needs while maintaining environmental resources and opportunities for future generations. Examples include energy efficiency, responsible water use, recycling, conservation of forests and adoption of suitable renewable energy sources.

5 Marks 18. Explain the role of ecosystems in maintaining environmental balance.

Ecosystems contain producers, consumers and decomposers. Energy flows through food chains and food webs, while decomposition returns nutrients to the environment. These interactions help maintain ecosystem functions and dynamic balance.

5 Marks 19. Explain five methods of sustainable resource management.

Methods include reducing unnecessary consumption, reusing materials, recycling, conserving water and energy, protecting forests and biodiversity, and using renewable resources responsibly.

5 Marks 20. Explain why uncontrolled exploitation of natural resources is harmful.

It can cause resource depletion, habitat destruction, pollution, soil degradation, biodiversity loss and ecological imbalance. It can also reduce resource availability for future generations.

6 Marks 21. Describe the importance of sustainable management in modern society.

Sustainable management helps conserve finite resources, protect ecosystems, reduce pollution, maintain biodiversity and support long-term human well-being. It encourages efficient resource use and considers environmental, economic and social needs together.

6 Marks 22. Explain the relationship between environment, development and sustainability.

Human development depends on natural resources and ecosystem services. However, excessive resource use and pollution can damage environmental systems. Sustainability seeks to maintain development and human well-being while conserving resources, protecting ecosystems and considering future generations.

6 Marks 23. Explain how individual actions can contribute to sustainable management.

Individuals can save electricity and water, reduce unnecessary consumption, reuse durable products, segregate waste, recycle suitable materials, avoid unnecessary single-use products, use public transport where practical and support conservation practices.

6 Marks 24. Explain biodiversity and its importance for sustainable ecosystems.

Biodiversity is the variety of life. Different organisms perform different ecological roles such as pollination, decomposition, predation and nutrient cycling. Biodiversity can improve ecosystem functioning and resilience and provides food, medicines and genetic resources.

6 Marks 25. Explain environmental conservation with suitable examples.

Environmental conservation means protecting and wisely managing nature. Examples include afforestation, protection of wildlife habitats, water conservation, soil conservation, pollution control, recycling and sustainable use of natural resources.

6 Marks 26. Explain the importance of the three Rs in waste management.

Reduce decreases waste at its source. Reuse extends the useful life of products. Recycling recovers materials from waste. Together these practices can reduce resource consumption, landfill pressure and pollution.

6 Marks 27. What is carrying capacity? Why is it important in environmental management?

Carrying capacity is the level of population or activity that an environment can support over time without unacceptable degradation. It is important because resources, space and ecological processes have limits.

6 Marks 28. Explain why renewable energy does not mean zero environmental impact.

Renewable sources such as solar, wind and hydropower reduce dependence on finite fuels but may require land, materials and infrastructure. They can also affect habitats, landscapes or wildlife depending on location and technology. Therefore, renewable resources also require responsible planning.

6 Marks 29. Explain the importance of environmental education.

Environmental education develops awareness about ecosystems, pollution, resource conservation and sustainable practices. It helps people make informed decisions and encourages responsible participation in environmental protection.

6 Marks 30. “Development and environmental conservation must be considered together.” Explain.

Development provides economic and social benefits, but natural resources and ecosystems support that development. If environmental degradation becomes severe, long-term benefits may be reduced. Sustainable planning therefore attempts to combine development with conservation and responsible resource use.

23. Assertion–Reason Questions

1. Assertion: Sustainable management considers future generations.
Reason: Natural resources are unlimited and can never be depleted.

Answer: Assertion is true, Reason is false.

2. Assertion: Biodiversity conservation is important for sustainable ecosystems.
Reason: Different organisms perform different ecological roles.

Answer: Both Assertion and Reason are true, and Reason correctly explains the Assertion.

3. Assertion: Renewable resources do not require any management.
Reason: All renewable resources are unlimited.

Answer: Both statements are false.

4. Assertion: Recycling can reduce pressure on natural resources.
Reason: Recycling can recover useful materials from waste.

Answer: Both Assertion and Reason are true, and Reason correctly explains the Assertion.

5. Assertion: Environmental conservation and development can be considered together.
Reason: Human development depends on natural resources and ecosystem services.

Answer: Both Assertion and Reason are true, and Reason correctly explains the Assertion.

24. HOTS Questions

HOTS 1: A village has sufficient rainfall but faces water shortage every summer. How can sustainable management help?

Rainwater harvesting, groundwater recharge, efficient irrigation, leak reduction and responsible water consumption can improve water availability and reduce wastage.

HOTS 2: A city recycles a large quantity of plastic but continues to generate increasing plastic waste. What additional approach is required?

Recycling alone is not sufficient. The city should also reduce unnecessary consumption, promote reuse and improve product/waste design and segregation.

HOTS 3: Why may cutting down a forest for short-term economic benefit create long-term problems?

Deforestation can cause habitat loss, biodiversity decline, soil erosion, changes in water cycles and loss of ecosystem services, potentially creating long-term ecological and economic costs.

HOTS 4: Why should renewable energy projects also undergo environmental planning?

Renewable projects may require land, materials and infrastructure and can affect habitats or wildlife depending on their location. Proper planning helps minimise these impacts.

HOTS 5: A school wants to become more environmentally sustainable. Suggest five actions.

Save electricity, conserve water, segregate waste, reduce single-use materials, recycle suitable waste, plant and protect vegetation, and educate students about responsible resource use.

25. One-Minute Revision

🌍 Environment: Biotic + Abiotic surroundings.

🌱 Ecosystem: Organisms + physical environment + interactions.

♻️ Conservation: Protection and wise management of resources.

🌿 Sustainability: Meet present needs while maintaining future opportunities.

🔄 Reduce: Consume less and generate less waste.

♻️ Reuse: Use products again.

🔁 Recycle: Recover useful materials from waste.

🐾 Biodiversity: Variety of life.

👨‍👩‍👧‍👦 Intergenerational Equity: Consider future generations.

💧 Resource Conservation: Use natural resources efficiently and responsibly.

26. Golden Points for CBSE Exam

1. Environment contains both biotic and abiotic components.

2. Ecosystem is a functional unit involving organisms and their physical environment.

3. Sustainable management does not mean stopping development; it means managing development and resources responsibly.

4. Renewable resources are not necessarily impact-free.

5. Biodiversity conservation is important for healthy ecosystems.

6. Reduce, Reuse and Recycle help reduce waste and resource consumption.

7. Future generations must be considered in resource-management decisions.

8. Environmental, economic and social dimensions are interconnected in sustainable development.

27. Quick Answer Key – 30 MCQs

Q	Ans	Q	Ans	Q	Ans
1	C	11	B	21	B
2	A	12	D	22	A
3	D	13	C	23	C
4	B	14	A	24	B
5	A	15	C	25	A
6	C	16	B	26	A
7	B	17	D	27	D
8	A	18	A	28	A
9	D	19	B	29	B
10	C	20	C	30	C

Class 10 CBSE Science
Our Environment and Sustainable Management | Introduction and Importance
CBSE • Foundation • Competitive Preparation

Class 10th Science Chapter 14 – Sources of Energy | Important Definitions and Key Concepts

Class 10 Science – Chapter 14

Sources of Energy | Important Definitions and Key Concepts

महत्वपूर्ण परिभाषाएँ • मुख्य अवधारणाएँ • Formula • Examples • Revision

⚡ Sources of Energy | Important Definitions and Key Concepts

1. Energy – ऊर्जा

Energy: The capacity to do work is called energy.

हिंदी: कार्य करने की क्षमता को ऊर्जा कहते हैं।

SI Unit: Joule (J)
Important Point: Energy can neither be created nor destroyed; it can only be transformed from one form to another.

2. Source of Energy – ऊर्जा का स्रोत

Source of Energy: A natural or artificial source from which useful energy can be obtained is called a source of energy.

हिंदी: वह प्राकृतिक या कृत्रिम स्रोत जिससे उपयोगी ऊर्जा प्राप्त की जा सकती है, ऊर्जा का स्रोत कहलाता है।

Examples: Sun, wind, water, biomass, coal, petroleum, natural gas, uranium.

3. Renewable Source – नवीकरणीय ऊर्जा स्रोत

Renewable Energy Source: An energy source that is naturally replenished on a useful human time scale is called a renewable source.

हिंदी: ऐसा ऊर्जा स्रोत जो प्राकृतिक प्रक्रियाओं द्वारा मानव जीवन के उपयोगी समय-मान पर पुनः उपलब्ध होता रहता है, नवीकरणीय स्रोत कहलाता है।

Examples: Solar energy, wind energy, hydropower, tidal energy, wave energy and geothermal energy.

4. Non-renewable Source – अनवीकरणीय ऊर्जा स्रोत

Non-renewable Energy Source: A source available in limited reserves and not replenished rapidly enough for human use is called a non-renewable source.

हिंदी: ऐसा ऊर्जा स्रोत जिसकी मात्रा सीमित होती है और जो मानव उपयोग की गति के अनुसार शीघ्र पुनः उपलब्ध नहीं होता, अनवीकरणीय स्रोत कहलाता है।

Examples: Coal, petroleum, natural gas and nuclear fuels such as uranium.

5. Solar Energy – सौर ऊर्जा

Solar Energy: The energy received from the Sun in the form of electromagnetic radiation is called solar energy.

हिंदी: सूर्य से विद्युतचुंबकीय विकिरण के रूप में प्राप्त ऊर्जा को सौर ऊर्जा कहते हैं।

Solar energy can be converted into:
☀ Heat energy → Solar cooker / Solar water heater
☀ Electrical energy → Solar cell / Solar panel

6. Solar Cooker – सौर कुकर

Solar Cooker: A device that uses solar radiation mainly to produce heat for cooking is called a solar cooker.

हिंदी: सौर विकिरण का उपयोग करके भोजन पकाने के लिए ऊष्मा उत्पन्न करने वाले उपकरण को सौर कुकर कहते हैं।

Important features:

• Black surface absorbs more solar radiation.
• Glass cover helps trap heat.
• Insulation reduces heat loss.
• Reflector can direct additional sunlight into the cooker.

7. Solar Cell – सौर सेल

Solar Cell: A semiconductor device that converts solar radiation directly into electrical energy is called a solar cell.

हिंदी: सौर विकिरण को सीधे विद्युत ऊर्जा में बदलने वाले semiconductor device को सौर सेल कहते हैं।

Also called: Photovoltaic cell / PV cell.
Common semiconductor: Silicon.

8. Photovoltaic Effect – फोटोवोल्टिक प्रभाव

Photovoltaic Effect: The generation of an electrical potential difference and current in a semiconductor due to incident light is known as the photovoltaic effect.

हिंदी: प्रकाश के semiconductor पर पड़ने से विद्युत विभवांतर तथा विद्युत धारा उत्पन्न होने की घटना को फोटोवोल्टिक प्रभाव कहते हैं।

9. Solar Panel – सौर पैनल

Solar Panel: A module containing several interconnected solar cells is called a solar panel.

हिंदी: अनेक interconnected solar cells से बने module को solar panel कहते हैं।

Remember: Solar Cell = individual unit; Solar Panel/Module = many connected cells.

10. Wind Energy – पवन ऊर्जा

Wind Energy: The kinetic energy possessed by moving air is called wind energy.

हिंदी: गतिशील वायु में उपस्थित गतिज ऊर्जा को पवन ऊर्जा कहते हैं।

11. Wind Turbine – पवन टर्बाइन

Wind Turbine: A machine that converts the kinetic energy of wind into mechanical energy and usually electrical energy through a generator is called a wind turbine.

हिंदी: पवन की गतिज ऊर्जा को यांत्रिक तथा आगे विद्युत ऊर्जा में बदलने वाली मशीन को wind turbine कहते हैं।

Wind → Turbine → Generator → Electrical Energy

12. Wind Farm – पवन ऊर्जा फार्म

Wind Farm: A group of wind turbines installed over a suitable area for electricity generation is called a wind farm.

हिंदी: किसी उपयुक्त क्षेत्र में विद्युत उत्पादन के लिए स्थापित अनेक wind turbines के समूह को wind farm कहते हैं।

13. Hydroelectric Energy – जलविद्युत ऊर्जा

Hydroelectric Energy: Electrical energy generated using the energy of flowing or falling water is called hydroelectric energy.

हिंदी: बहते या गिरते हुए जल की ऊर्जा का उपयोग करके उत्पन्न विद्युत ऊर्जा को जलविद्युत ऊर्जा कहते हैं।

Potential Energy of Water → Kinetic Energy → Turbine → Generator → Electricity

14. Hydroelectric Power Plant – जलविद्युत संयंत्र

Hydroelectric Power Plant: A power station that generates electricity using flowing or falling water is called a hydroelectric power plant.

Main components: Reservoir/Dam → Water channel → Turbine → Generator → Electricity

15. Biomass – जैवभार

Biomass: Organic material obtained from plants, animals and their wastes that can be used as an energy source is called biomass.

हिंदी: पौधों, जानवरों तथा उनके अपशिष्टों से प्राप्त जैविक पदार्थ जिसे ऊर्जा स्रोत के रूप में उपयोग किया जा सकता है, biomass कहलाता है।

Examples: Wood, crop residues, animal dung and other organic wastes.

16. Biogas – बायोगैस

Biogas: A combustible gas mixture produced by anaerobic decomposition of organic matter is called biogas.

हिंदी: जैविक पदार्थों के anaerobic decomposition से बनने वाली ज्वलनशील गैस मिश्रण को biogas कहते हैं।

Major combustible component: Methane (CH₄)
Other gases may include carbon dioxide and small amounts of other gases.

17. Anaerobic Decomposition – अवायवीय अपघटन

Anaerobic Decomposition: Breakdown of organic matter by microorganisms in the absence of oxygen is called anaerobic decomposition.

हिंदी: ऑक्सीजन की अनुपस्थिति में microorganisms द्वारा organic matter के breakdown को anaerobic decomposition कहते हैं।

18. Tidal Energy – ज्वारीय ऊर्जा

Tidal Energy: Energy obtained from the periodic rise, fall and movement of ocean water is called tidal energy.

हिंदी: समुद्री जल के periodic rise, fall तथा movement से प्राप्त ऊर्जा को tidal energy कहते हैं।

The tides are mainly associated with the gravitational effects of the Moon and the Sun.

19. Tidal Barrage – ज्वारीय बाँध

Tidal Barrage: A barrier constructed across a suitable tidal area to capture water movement and operate turbines is called a tidal barrage.

20. Wave Energy – तरंग ऊर्जा

Wave Energy: Energy contained in the motion of ocean surface waves is called wave energy.

हिंदी: समुद्र की सतही तरंगों की गति में निहित ऊर्जा को wave energy कहते हैं।

Ocean waves mainly obtain their energy from wind. Wave-energy devices convert wave motion into useful energy.

21. Geothermal Energy – भू-तापीय ऊर्जा

Geothermal Energy: Energy obtained from the internal heat of the Earth is called geothermal energy.

हिंदी: पृथ्वी के आंतरिक भाग की ऊष्मा से प्राप्त ऊर्जा को geothermal energy कहते हैं।

Examples: Hot springs, geothermal steam and geothermal power plants.

22. Nuclear Energy – नाभिकीय ऊर्जा

Nuclear Energy: Energy released from changes in atomic nuclei, such as nuclear fission, is called nuclear energy.

हिंदी: परमाणु नाभिक में होने वाले परिवर्तन, जैसे nuclear fission, से मुक्त ऊर्जा को nuclear energy कहते हैं।

23. Nuclear Fission – नाभिकीय विखंडन

Nuclear Fission: The splitting of a heavy atomic nucleus into smaller nuclei with release of energy is called nuclear fission.

हिंदी: भारी atomic nucleus के छोटे nuclei में टूटने तथा ऊर्जा निकलने की प्रक्रिया को nuclear fission कहते हैं।

Heavy Nucleus + Neutron → Smaller Nuclei + Energy + Neutrons

24. Nuclear Reactor – नाभिकीय रिएक्टर

Nuclear Reactor: A device in which a controlled nuclear fission chain reaction is maintained to release useful energy is called a nuclear reactor.

Important parts may include:
Fuel → Moderator → Control Rods → Coolant → Heat-transfer system

25. Chain Reaction – श्रृंखला अभिक्रिया

Chain Reaction: A sequence in which neutrons released during one fission event cause further fission events is called a nuclear chain reaction.

In a nuclear reactor, the chain reaction is controlled so that heat is released at a manageable rate.

26. Energy Density – ऊर्जा घनत्व

Energy Density: The amount of energy available per unit mass or unit volume of a fuel or source is called energy density.

हिंदी: प्रति unit mass या unit volume उपलब्ध ऊर्जा की मात्रा को energy density कहते हैं।

Nuclear fuels have very high energy density compared with many conventional fuels.

27. Fossil Fuels – जीवाश्म ईंधन

Fossil Fuels: Fuels formed over geological time from the remains of ancient organisms and containing stored chemical energy are called fossil fuels.

Examples: Coal, petroleum and natural gas.

28. Fuel – ईंधन

Fuel: A substance that releases useful energy, usually heat, through a chemical or nuclear process is called a fuel.

29. Calorific Value – ऊष्मीय मान

Calorific Value: The amount of heat released by complete combustion of a unit quantity of fuel is called its calorific value.

हिंदी: fuel की unit quantity के complete combustion से प्राप्त heat energy को calorific value कहते हैं।

Common unit: kJ/kg for solid and liquid fuels.

30. Efficiency – दक्षता

Efficiency: The ratio of useful output energy to input energy, expressed as a percentage, is called efficiency.

Efficiency = (Useful Output Energy / Input Energy) × 100

31. Energy Conversion – ऊर्जा रूपांतरण

Energy Conversion: The transformation of energy from one form to another is called energy conversion.

हिंदी: ऊर्जा का एक रूप से दूसरे रूप में परिवर्तन energy conversion कहलाता है।

System	Energy Conversion
Solar Cell	Solar → Electrical
Solar Cooker	Solar → Heat
Wind Turbine	Wind Kinetic → Mechanical → Electrical
Hydroelectric Plant	Potential → Kinetic → Mechanical → Electrical
Biogas	Chemical Energy → Heat / Useful Energy
Nuclear Plant	Nuclear → Heat → Mechanical → Electrical

32. Power – शक्ति

Power: The rate at which energy is transferred or work is done is called power.

Power = Energy / Time
P = E/t

SI Unit: Watt (W)

33. Sustainable Energy – सतत ऊर्जा

Sustainable Energy: Energy use and production that can meet present needs while reducing long-term resource depletion and environmental damage is generally described as sustainable energy use.

Sustainable energy planning considers availability, affordability, reliability, efficiency and environmental effects.

34. Energy Conservation – ऊर्जा संरक्षण

Energy Conservation: The reduction of unnecessary energy consumption through efficient use and avoidance of wastage is called energy conservation.

हिंदी: ऊर्जा की अनावश्यक खपत तथा wastage को कम करना energy conservation कहलाता है।

Examples:
• Switching off unused appliances
• Using energy-efficient devices
• Using public transport where practical
• Improving insulation
• Avoiding unnecessary fuel consumption

35. Energy Efficiency – ऊर्जा दक्षता

Energy Efficiency: Obtaining the same useful service with less energy input, or obtaining more useful output from the same input, is called energy efficiency.

Conservation focuses on reducing unnecessary use; efficiency focuses on getting more useful output from energy input.

36. Greenhouse Gas – ग्रीनहाउस गैस

Greenhouse Gases: Gases that absorb and re-emit infrared radiation and contribute to the greenhouse effect are called greenhouse gases.

Examples include carbon dioxide (CO₂), methane (CH₄), water vapour and nitrous oxide (N₂O).

37. Greenhouse Effect – ग्रीनहाउस प्रभाव

Greenhouse Effect: The warming of Earth’s surface and lower atmosphere due to absorption and re-emission of infrared radiation by greenhouse gases is called the greenhouse effect.

38. Carbon Footprint – कार्बन फुटप्रिंट

Carbon Footprint: The total greenhouse-gas emissions associated with an activity, product, person or organisation, usually expressed as CO₂-equivalent, are referred to as its carbon footprint.

39. Pollution – प्रदूषण

Pollution: The undesirable contamination or alteration of the environment that can harm organisms, ecosystems or resources is called pollution.

Energy production may cause air, water, soil, thermal or other environmental impacts depending on the technology.

40. Renewable ≠ Impact-Free

Important Concept:

Renewable energy sources are replenished naturally, but they are not necessarily completely free from environmental impacts.

For example, hydroelectric projects can alter river ecosystems, wind projects can affect land and wildlife, and solar installations require materials and land.

41. Primary Energy – प्राथमिक ऊर्जा

Primary Energy: Energy available directly from natural resources before human conversion into another form is called primary energy.

Examples: Solar radiation, coal, crude oil, natural gas, wind and flowing water.

42. Secondary Energy – द्वितीयक ऊर्जा

Secondary Energy: Energy obtained after conversion or processing of primary energy into a more useful form is called secondary energy.

Example: Electricity generated from coal, water, wind, solar or nuclear energy.

43. Intermittent Source – रुक-रुक कर उपलब्ध स्रोत

Intermittent Energy Source: An energy source whose availability or output naturally varies with time is called intermittent.

Solar and wind output can vary with sunlight and wind conditions.

44. Base Load – आधारभूत विद्युत मांग

Base Load: The minimum continuous level of electrical power demand that a power system needs to supply over a period is called base load.

45. Energy Storage – ऊर्जा भंडारण

Energy Storage: The process of storing energy for use at a later time is called energy storage.

Examples: Batteries, pumped-storage hydropower and thermal storage.

46. Important Key Concepts – मुख्य अवधारणाएँ

Concept	Key Point
Solar Cell	Solar radiation → Electrical energy.
Solar Cooker	Solar radiation → Heat.
Wind	Kinetic energy of moving air.
Hydro	Uses energy of falling/flowing water.
Biogas	Anaerobic decomposition; methane is major combustible component.
Tidal	Periodic ocean-water movement.
Wave	Energy of ocean surface waves.
Geothermal	Earth’s internal heat.
Nuclear Fission	Splitting of a heavy nucleus with energy release.
Renewable	Naturally replenished on useful human time scales.
Non-renewable	Limited reserves; not rapidly replenished.
Efficiency	Useful output / input × 100.
Energy Conservation	Reduce unnecessary energy use and wastage.

47. Important MCQs – 30 Questions

Q1. The SI unit of energy is:

A) Watt

B) Joule

C) Volt

D) Newton

Answer: B

Q2. Which is a renewable energy source?

A) Coal

B) Petroleum

C) Solar energy

D) Natural gas

Answer: C

Q3. A solar cell converts:

A) Solar energy into electrical energy

B) Electrical energy into solar energy

C) Heat into coal

D) Sound into light

Answer: A

Q4. The photovoltaic effect is associated with:

A) Wind turbines

B) Solar cells

C) Hydroelectric dams

D) Nuclear reactors

Answer: B

Q5. Wind energy is mainly the:

A) Potential energy of water

B) Kinetic energy of moving air

C) Nuclear energy of air

D) Chemical energy of oxygen

Answer: B

Q6. Biogas is produced mainly through:

A) Aerobic combustion

B) Anaerobic decomposition

C) Nuclear fission

D) Photosynthesis

Answer: B

Q7. The major combustible component of biogas is:

A) Oxygen

B) Nitrogen

C) Methane

D) Carbon monoxide

Answer: C

Q8. Tidal energy is related mainly to:

A) Ocean tides

B) Underground heat

C) Coal burning

D) Solar cells

Answer: A

Q9. Wave energy is obtained from:

A) Ocean surface waves

B) Coal seams

C) Earthquakes only

D) Nuclear reactions

Answer: A

Q10. Geothermal energy is obtained from:

A) Moonlight

B) Earth’s internal heat

C) Wind

D) Petroleum

Answer: B

Q11. Nuclear fission means:

A) Joining light nuclei

B) Splitting a heavy nucleus

C) Burning coal

D) Evaporation of water

Answer: B

Q12. Which is non-renewable?

A) Wind

B) Solar

C) Coal

D) Tidal

Answer: C

Q13. The ratio of useful output energy to input energy is related to:

A) Efficiency

B) Frequency

C) Resistance

D) Pressure

Answer: A

Q14. Energy conservation mainly means:

A) Creating energy

B) Reducing unnecessary energy use

C) Destroying energy

D) Producing coal

Answer: B

Q15. Which is a fossil fuel?

A) Coal

B) Wind

C) Solar

D) Tidal

Answer: A

Q16. Which source is associated with Earth’s internal heat?

A) Wave

B) Geothermal

C) Wind

D) Biomass

Answer: B

Q17. A wind farm consists of:

A) Many wind turbines

B) Many solar cookers

C) Many dams

D) Many nuclear reactors

Answer: A

Q18. Which is a primary energy source?

A) Electricity

B) Solar radiation

C) Refined electricity

D) Battery output

Answer: B

Q19. Electricity generated from a power plant is generally considered:

A) Secondary energy

B) Primary sunlight

C) Raw biomass

D) Fossil fuel

Answer: A

Q20. Which source can be intermittent because its output depends on sunlight?

A) Solar

B) Nuclear

C) Geothermal

D) Coal

Answer: A

Q21. The rate of energy transfer is called:

A) Power

B) Work

C) Density

D) Voltage

Answer: A

Q22. Which gas is a greenhouse gas?

A) Carbon dioxide

B) Oxygen

C) Helium

D) Argon only

Answer: A

Q23. Calorific value refers to:

A) Heat released by a unit quantity of fuel on complete combustion

B) Mass of a fuel

C) Volume of a turbine

D) Speed of wind

Answer: A

Q24. Which is an example of energy storage?

A) Battery

B) Wind

C) Sunlight

D) Coal mine

Answer: A

Q25. Which statement is correct?

A) Renewable means zero environmental impact

B) Renewable sources can still have environmental impacts

C) Coal is renewable

D) Solar cells require coal combustion

Answer: B

Q26. Which source uses gravitational potential energy of water?

A) Hydroelectric

B) Solar

C) Wind

D) Geothermal

Answer: A

Q27. A solar panel is generally:

A) A group of interconnected solar cells

B) A coal-burning machine

C) A wind turbine

D) A nuclear reactor

Answer: A

Q28. The major purpose of energy efficiency is to:

A) Obtain useful service with less energy input

B) Waste more energy

C) Increase fuel consumption

D) Eliminate all energy sources

Answer: A

Q29. Which is an example of a secondary energy form?

A) Electricity

B) Sunlight

C) Crude oil

D) Coal

Answer: A

Q30. Which statement best describes sustainable energy planning?

A) Consider only cost

B) Consider resources, reliability, efficiency and environmental effects

C) Use only coal

D) Avoid all renewable sources

Answer: B

48. Subjective Questions – 30 Questions

2 Marks Q1. Define energy.

Energy is the capacity to do work. Its SI unit is joule.

2 Marks Q2. Define renewable energy source.

A source that is naturally replenished on a useful human time scale is called renewable.

2 Marks Q3. What is a solar cell?

A semiconductor device that converts solar radiation directly into electrical energy.

2 Marks Q4. What is wind energy?

Wind energy is the kinetic energy possessed by moving air.

2 Marks Q5. Define biomass.

Biomass is organic material from plants, animals and their wastes that can be used as an energy source.

2 Marks Q6. What is biogas?

Biogas is a combustible gas mixture produced by anaerobic decomposition of organic matter.

3 Marks Q7. Define tidal energy and state its cause.

Tidal energy is obtained from periodic ocean-water movement. It is mainly associated with gravitational effects of the Moon and Sun.

3 Marks Q8. What is wave energy?

Wave energy is the energy present in the motion of ocean surface waves. Ocean waves mainly obtain their energy from wind.

3 Marks Q9. Define geothermal energy.

Geothermal energy is energy obtained from the internal heat of Earth.

3 Marks Q10. Define nuclear fission.

Nuclear fission is the splitting of a heavy atomic nucleus into smaller nuclei with release of energy.

3 Marks Q11. What is a nuclear reactor?

A nuclear reactor is a device in which a controlled nuclear fission chain reaction is maintained to release useful energy.

3 Marks Q12. Define energy efficiency.

Energy efficiency means obtaining the same useful service with less energy input, or obtaining more useful output from the same input.

4 Marks Q13. Differentiate between renewable and non-renewable sources.

Renewable sources are naturally replenished, such as solar and wind. Non-renewable sources have limited reserves and are not replenished rapidly, such as coal and petroleum.

4 Marks Q14. Define photovoltaic effect and state its application.

The photovoltaic effect is the generation of electrical potential/current in a semiconductor due to incident light. It is used in solar cells.

4 Marks Q15. Explain energy conversion in a hydroelectric plant.

Water stored at height has gravitational potential energy. Falling water gains kinetic energy and rotates a turbine. The generator converts mechanical energy into electrical energy.

4 Marks Q16. Explain the term energy conservation.

Energy conservation means reducing unnecessary energy consumption and avoiding wastage through efficient practices and responsible use.

4 Marks Q17. What is the greenhouse effect?

The greenhouse effect is warming associated with absorption and re-emission of infrared radiation by greenhouse gases in the atmosphere.

4 Marks Q18. Define carbon footprint.

Carbon footprint refers to greenhouse-gas emissions associated with an activity, product, person or organisation, commonly expressed as CO₂-equivalent.

5 Marks Q19. Explain solar energy and its two major applications.

Solar energy is energy received from the Sun. It can be converted into heat using solar cookers and into electricity using photovoltaic cells. Solar energy is renewable but depends on sunlight availability.

5 Marks Q20. Explain biomass and biogas.

Biomass includes organic materials such as wood, crop residues and animal waste. Anaerobic decomposition of suitable biomass can produce biogas, whose major combustible component is methane.

5 Marks Q21. Explain wind energy and wind turbine.

Wind energy is the kinetic energy of moving air. Wind turbine blades rotate due to wind, converting wind energy into mechanical energy, which is then converted into electrical energy by a generator.

5 Marks Q22. Explain nuclear energy and nuclear fission.

Nuclear energy can be released through changes in atomic nuclei. In fission, a heavy nucleus splits into smaller nuclei and releases energy and neutrons. Controlled fission is used in nuclear reactors.

5 Marks Q23. What is the difference between energy conservation and energy efficiency?

Energy conservation reduces unnecessary energy use and wastage. Energy efficiency improves the amount of useful service or output obtained from a given amount of energy.

6 Marks Q24. Explain six important renewable energy sources.

Solar energy comes from the Sun. Wind energy comes from moving air. Hydroelectric energy uses falling/flowing water. Tidal energy uses ocean tides. Wave energy uses ocean surface waves. Geothermal energy uses Earth’s internal heat. Biomass is another renewable resource when sustainably managed.

6 Marks Q25. Explain the important energy conversions in Chapter 14.

Solar cell: Solar → Electrical.
Solar cooker: Solar → Heat.
Wind turbine: Wind kinetic → Mechanical → Electrical.
Hydroelectric plant: Potential → Kinetic → Mechanical → Electrical.
Nuclear plant: Nuclear → Heat → Mechanical → Electrical.

6 Marks Q26. Explain primary and secondary energy.

Primary energy is available directly from natural resources such as sunlight, coal, wind and flowing water. Secondary energy is obtained after conversion or processing, such as electricity generated from different primary sources.

6 Marks Q27. Explain intermittent energy sources with examples.

An intermittent source has naturally variable output or availability. Solar output varies with day/night and weather, while wind output varies with wind conditions. Storage, backup or grid management may help balance supply and demand.

6 Marks Q28. Why should renewable energy not be considered completely impact-free?

Renewable technologies still require materials, land, construction and infrastructure. They can have effects on habitats, landscapes, water systems, wildlife or waste streams depending on the technology and location.

6 Marks Q29. Explain the importance of sustainable energy planning.

Sustainable planning considers resource availability, reliability, efficiency, affordability and environmental effects. It aims to meet energy needs while reducing long-term depletion and environmental damage.

6 Marks Q30. Write a comprehensive revision note on Sources of Energy.

Energy sources may be renewable or non-renewable. Solar, wind, hydro, biomass, tidal, wave and geothermal are important renewable sources. Coal, petroleum and natural gas are fossil fuels. Nuclear fission provides nuclear energy. Important concepts include energy conversion, efficiency, conservation, energy storage, sustainability and environmental consequences.

49. Assertion–Reason

Q1. Assertion: Solar energy is renewable.
Reason: Solar radiation is continuously supplied by the Sun.

Answer: Both A and R are true, and R correctly explains A.

Q2. Assertion: Solar cells convert solar energy directly into electricity.
Reason: Solar cells use the photovoltaic effect.

Answer: Both A and R are true, and R correctly explains A.

Q3. Assertion: Coal is a renewable source.
Reason: Coal forms very rapidly.

Answer: Both A and R are false.

Q4. Assertion: Biogas can be produced from organic waste.
Reason: Anaerobic microorganisms decompose organic matter.

Answer: Both A and R are true, and R correctly explains A.

Q5. Assertion: Renewable sources have no environmental impact.
Reason: Renewable resources are naturally replenished.

Answer: Assertion is false, while Reason is true.

50. HOTS – Higher Order Thinking

Q1. Why is solar energy renewable but not necessarily available continuously at a fixed location?

Solar energy is continuously supplied by the Sun on human time scales, but a location receives varying sunlight because of night, clouds, seasons and weather.

Q2. Why does a solar cell and solar cooker produce different useful outputs from the same source?

They use different conversion mechanisms and designs. A solar cell uses photovoltaic conversion to generate electricity, while a solar cooker absorbs radiation and converts it mainly into heat.

Q3. Why is energy efficiency important even when renewable energy is available?

Efficiency reduces the amount of energy required for a useful service. This reduces system size, resource requirements, losses and often costs and environmental impacts.

Q4. Why can tidal energy be predictable but still geographically limited?

Tides follow predictable astronomical cycles, but only locations with suitable tidal range, currents, coastal geometry and engineering conditions can economically capture the energy.

Q5. Why is nuclear fuel described as having high energy density?

A relatively small mass of nuclear fuel can release a very large amount of energy through nuclear reactions compared with the chemical energy released by many conventional fuels.

51. Formula & Fact Box

Efficiency = Useful Output / Input × 100

Power = Energy / Time

Quick Facts:

1. Solar cell → Photovoltaic effect.
2. Wind → Kinetic energy of moving air.
3. Hydro → Gravitational potential energy of water.
4. Biogas → Anaerobic decomposition.
5. Tidal → Ocean tides.
6. Wave → Ocean surface waves.
7. Geothermal → Earth’s internal heat.
8. Nuclear fission → Splitting of heavy nucleus.
9. Renewable → Naturally replenished.
10. Non-renewable → Limited reserves.

52. One-Minute Revision

ENERGY

↓

Renewable → Solar • Wind • Hydro • Biomass • Tidal • Wave • Geothermal

Non-renewable → Coal • Petroleum • Natural Gas • Nuclear Fuel

Solar Cell → Solar → Electrical

Wind Turbine → Wind → Mechanical → Electrical

Hydro → Potential → Kinetic → Mechanical → Electrical

Nuclear → Fission → Heat → Mechanical → Electrical

Efficiency → Useful Output / Input × 100

Conservation → Reduce unnecessary energy use

53. Final Exam Golden Points

✔ Energy = capacity to do work.

✔ SI unit of energy = Joule.

✔ Renewable sources are naturally replenished on useful human time scales.

✔ Solar cell = photovoltaic device.

✔ Solar cooker = heat from solar radiation.

✔ Wind energy = kinetic energy of moving air.

✔ Hydroelectricity uses energy of falling/flowing water.

✔ Biogas is produced by anaerobic decomposition.

✔ Methane is the major combustible component of biogas.

✔ Tidal energy is associated with periodic ocean-water movement.

✔ Wave energy comes from ocean surface waves.

✔ Geothermal energy comes from Earth's internal heat.

✔ Nuclear fission = splitting of a heavy nucleus.

✔ Efficiency = useful output/input × 100.

✔ Renewable does not mean completely impact-free.

✔ Energy conservation reduces unnecessary energy consumption.

✔ Energy efficiency means more useful service/output from less energy input.

Class 10 CBSE Science – Chapter 14
Sources of Energy | Important Definitions and Key Concepts

⚡ Definitions • Concepts • Formula • Examples • MCQs • HOTS • Revision