What is the law of conservation of energy?

The law of conservation of energy is that energy cannot be created or destroyed but can be changed from one form to another.

How is energy connected with work?

Energy is needed to perform work, and the work done is equal to the energy transferred.

What is the energy efficiency of a system?

Energy efficiency is the measure of useful energy output in comparison to the input energy, usually given as a percentage.

What is the definition of Energy?

Energy is the ability to perform work or induce change in a system.

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Sources of Energy

1.0Master Fuel Dynamics, Power Generation, and Renewable Alternatives in Minutes

Unlock the thermodynamic principles powering global civilization. Learn to distinguish between dwindling fossil reserves and infinite natural energy flows, explore how traditional thermal and hydro plants convert kinetic forces into spinning electricity, and master the clean engineering physics behind solar cells, wind farms, and nuclear fission to ace your physics fundamentals.

Class: 10 Science (CBSE)
Chapter: Sources of Energy
Estimated Learning Time: 25–30 Minutes

2.0Learning Outcomes

After completing this lesson, you will be able to:

Identify the criteria that define a good, efficient source of fuel.
Contrast Conventional (Non-Renewable) and Non-Conventional (Renewable) sources of energy.
Diagram the mechanical energy transformations inside Thermal and Hydroelectric Power Plants.
Explain the operation of a fixed-dome Biomass Digester.
Analyze the engineering advantages and geographic limitations of Wind, Solar, and Tidal energy.
Describe the fundamental process of Nuclear Fission and discuss its environmental risks.

3.0Introduction to Sources of Energy

Welcome to the primary energy-management chapter of Class 10 Physics! According to the Law of Conservation of Energy, energy can neither be created nor destroyed—it can only be transformed from one form to another. If energy is always conserved, why do we constantly worry about an energy crisis? In this lesson, we answer this question by analyzing how usable energy degrades into unusable ambient heat during mechanical work. We will track traditional energy systems like coal combustion and hydroelectric dams, examine the environmental impacts of greenhouse gases, and explore clean, renewable alternatives like solar arrays, wind turbines, biomass recycling, and nuclear power.

Energy is the force that makes everything happen in the universe. From the rotation of planets in the Universe to the glow of a light bulb, energy drives our world in so many ways. It is available in many forms, such as the sun's heat and the spark of electricity, and is the key to life, technology, and advancement. The energy stored in food that powers our bodies or the energy produced by wind and solar systems to power our homes, understanding energy is the main component of designing a sustainable and innovative world.

4.0What is Energy?

Energy is the fundamental concept of science, which is defined as the ability to work to do work or cause change. It is present in various forms and can be transferred or converted from one form to another but can not be created. Energy is not always in a visible form but is always there at work. In simple words, energy is what things happen. Any physical, chemical, or biological process is not possible without energy.

In the international system of units, the energy unit is joules (J). Other commonly used units of energy are calories or kilowatt-hours (kWh).

5.0Types of Energy:

There are different types of energy in the universe, each connected with different sources and physical phenomena. Some common types of energy are:

Kinetic Energy: KE is the energy of motion. Any moving object, whether it's a car, a flying bird, or even a flowing river, possesses kinetic energy. The kinetic energy an object possesses depends directly on its mass(m) and velocity(v). The kinetic energy can expressed in terms of the following:

$K E = \frac{1}{2} m v^{2}$

Potential Energy: Potential energy (PE) is energy that is stored. It relies on the object's position or configuration. The most familiar one is gravitational potential energy, which relies on the height of an object above the ground. The potential energy formula can be expressed as:

$PE = m g h$

The Sum of both potential (PE) and kinetic energy (KE) is known as mechanical energy.

Solar Energy: It is a form of energy obtained from the light produced by the sun. Energy is a widely used form of energy due to its easy availability and unlimited source. This energy from the sun is further divided into different types of solar energy, which include:
- Solar Thermal Energy: It is used to produce heat for water or air heating and electricity generation.
- Photovoltaic Energy: Photovoltaic energy directly converts sunlight into electricity with the help of solar cells.
- Concentrated Solar Power: This is a type of solar energy which utilises mirrors or lenses to concentrate sunlight to produce high-temperature steam for the production of electricity.
Electrical Energy: Electrical energy is usually produced by the flow of electrons in a conductor. It energises devices from small devices such as smartphones to huge systems such as citywide electrical grids.
Nuclear Energy: Nuclear energy is contained within the nucleus of atoms. It is released by nuclear reactions like fission (atom splitting) or fusion (atom combining). This energy is utilised in nuclear power plants and the sun.

6.0Energy Density

Energy density can be defined as the amount of energy that is stored in a unit of volume or weight, the more the energy density, the more the energy is stored in the object. This concept of energy plays an important role in understanding renewable and non-renewable sources of energy. Solar wind and windmills have a lower energy density in comparison to fossil fuels. The formula for energy density can be stated as:

$E n er g yDe n s i t y = \frac{E n er g y St ore d}{V o l u m eor ma ss}$

Practically, energy density has applications in various objects, including batteries, fuel, and storage systems, where the space and weight of the object are important.

7.0Law of Conservation of Energy

The law of conservation of energy is the most famous and important law related to energy, which specifically states that “Energy can neither be created nor be destroyed and can only be converted from one form to another form”. In other words, the total amount of energy in any closed system remains constant over time. This law implies all types of energy irrespective of their source.

To understand this more clearly, imagine a pendulum in which potential energy is transferred to kinetic energy and vice versa. As the pendulum oscillates, the energy goes back and forth between these two forms, but the energy does not change. In real-life situations, some of the energy tends to be lost as heat due to friction, but the overall energy in the system is conserved.

8.0Solved Examples on Energy:

Problem: A pendulum with a bob of mass 0.5 kg is released from a height of 2 meters above its lowest point. Calculate the speed of the bob when it reaches the lowest point.

Solution: At the maximum height, the potential energy of the pendulum will be maximum, and the kinetic energy will be zero.

m = 0.5kg (mass of the bob)

g = 9.8 m/s² (acceleration due to gravity)

h = 2m

PE = mgh

PE = 0.59.82=9.8J

Now, Using the law of conservation of energy:

PE_initial = PE_final

$9.8 J = \frac{1}{2} \times 0.5 \times v^{2}$

$v^{2} = \frac{19.6}{0.5} = 39.2$

$v = 39.2 \approx 6.26 m/s$

Problem 2: A ball is dropped from a height of 10 meters. After bouncing, it reaches a height of 6 meters. Assuming energy loss due to air resistance and ground friction, calculate the energy lost in the bounce.

Solution: Before the bounce,

The Potential energy of the ball at 10 meters = mgh

PE_Initial = mgh

$PE_{Initial} = 1 \times 9.8 \times 10 = 98 J$

After the bounce at 6 meters:

The final potential energy at 6m = mgh

$PE_{Final} = m g h$

$PE_{Final} = 1 \times 9.8 \times 6 = 58.8 J$

The energy lost during the bounce:

$PE_{Initial} - PE_{Final} = 98 - 58.8 = 39.2 J$

Problem 3: An electric motor lifts a 10 kg weight to a height of 12 meters in 5 seconds. What is the power required by the motor?

Solution: Given m = 10kg, h = 12m, t = 5seconds

To calculate the power, firstly, we would calculate the work done, which is the same as the energy used, by using the formula:

PE = mgh

$PE = 10 \times 9.8 \times 12$

PE = 1,176 J

The formula for power $P = \frac{E}{t}$

$P = \frac{1176}{5} = 235.2 W$

9.0Important topics in Class 10 Science: Energy

Renewable & non-renewable energy sources

10.0EUREKA by ALLEN – The Future of Class 10 Learning

With EUREKA by ALLEN, you're going to change the way you learn as a Class 10 student using an AI-based educational platform designed just for you! EUREKA offers everything from online videos, customized learning paths, immediate question resolution, and live statistics about how well you are doing with ALLEN's educational professional discipline combined with advanced technology for a more intelligent and effective learning experience!

Interactive concept-based learning Story-driven video lessons Board exam-oriented preparation Subjective answer writing practice Instant quizzes and performance feedback Real-time progress monitoring AI-powered doubt support available 24×7 NCERT & CBSE-aligned curriculum Flexible on-demand learning access

Explore Now

11.0Supporting Study Materials

This study material, focusing on Energy Sources and Environmental Engineering, is structured according to the latest NCERT guidelines. Complete with step-by-step energy conversion paths, biogas digester cross-sections, and high-yield subjective questions, this guide ensures absolute confidence for your school assessments and board examinations.

CBSE Class 10 Science Notes Chapter 13 Our Environment	NCERT Solution Class 10 Science Chapter 13: Our Environment

30-Second Quick Review: Sources of Energy

✔ A good source of energy should have a high calorific value and cause minimum pollution.

✔ Renewable sources can be naturally replenished.

✔ Coal, petroleum, and natural gas are non-renewable resources.

✔ Solar energy is clean, renewable, and sustainable.

✔ Wind energy converts the kinetic energy of moving air into electricity.

✔ Hydroelectric power uses the potential energy of stored water.

✔ Biomass is obtained from plant and animal waste.

✔ Biogas is mainly composed of methane.

✔ Nuclear energy is obtained through nuclear fission.

✔ Fossil fuels contribute to global warming and air pollution.

✔ Renewable energy helps conserve natural resources and reduce environmental damage.

12.0Previous Year Questions (PYQs) on Sources of Energy

Q1. What are the qualities of an ideal source of energy? (CBSE Board)

Answer: Qualities of an Ideal Source of Energy: An excellent, highly efficient fuel source must satisfy the following criteria:

High Calorific Value: It must yield a large amount of usable heat energy per unit mass or volume.
Low Pollution: It should not emit toxic gases, thick smoke, or leave behind large amounts of ash upon combustion.
Economic & Accessible: It must be easy to locate, extract, and transport safely without massive infrastructure costs.
Controlled Combustion: It should burn at a steady, manageable rate rather than causing an uncontrolled explosion.

13.0Recommended Next Topics

Electricity
Magnetic Effects of Electric Current
Human Eye and the Colourful World
Chemical Reactions and Equations

Join ALLEN!

(Session 2026 - 27)

Name

Mobile Number

Class

Choose class

Goal

Choose your goal

Preferred Programs

Preferred Mode

State

Choose State

I agree to

I authorise ALLEN Career Institute Pvt Ltd to send me regular updates via Phone calls, Whatsapp, SMS, Robocalls (Automated Calls), Emails, or on postal address.

Sources of Energy

1.0Master Fuel Dynamics, Power Generation, and Renewable Alternatives in Minutes

Unlock the thermodynamic principles powering global civilization. Learn to distinguish between dwindling fossil reserves and infinite natural energy flows, explore how traditional thermal and hydro plants convert kinetic forces into spinning electricity, and master the clean engineering physics behind solar cells, wind farms, and nuclear fission to ace your physics fundamentals.

Class: 10 Science (CBSE)
Chapter: Sources of Energy
Estimated Learning Time: 25–30 Minutes

2.0Learning Outcomes

After completing this lesson, you will be able to:

Identify the criteria that define a good, efficient source of fuel.
Contrast Conventional (Non-Renewable) and Non-Conventional (Renewable) sources of energy.
Diagram the mechanical energy transformations inside Thermal and Hydroelectric Power Plants.
Explain the operation of a fixed-dome Biomass Digester.
Analyze the engineering advantages and geographic limitations of Wind, Solar, and Tidal energy.
Describe the fundamental process of Nuclear Fission and discuss its environmental risks.

3.0Introduction to Sources of Energy

Welcome to the primary energy-management chapter of Class 10 Physics! According to the Law of Conservation of Energy, energy can neither be created nor destroyed—it can only be transformed from one form to another. If energy is always conserved, why do we constantly worry about an energy crisis? In this lesson, we answer this question by analyzing how usable energy degrades into unusable ambient heat during mechanical work. We will track traditional energy systems like coal combustion and hydroelectric dams, examine the environmental impacts of greenhouse gases, and explore clean, renewable alternatives like solar arrays, wind turbines, biomass recycling, and nuclear power.

Energy is the force that makes everything happen in the universe. From the rotation of planets in the Universe to the glow of a light bulb, energy drives our world in so many ways. It is available in many forms, such as the sun's heat and the spark of electricity, and is the key to life, technology, and advancement. The energy stored in food that powers our bodies or the energy produced by wind and solar systems to power our homes, understanding energy is the main component of designing a sustainable and innovative world.

4.0What is Energy?

Energy is the fundamental concept of science, which is defined as the ability to work to do work or cause change. It is present in various forms and can be transferred or converted from one form to another but can not be created. Energy is not always in a visible form but is always there at work. In simple words, energy is what things happen. Any physical, chemical, or biological process is not possible without energy.

In the international system of units, the energy unit is joules (J). Other commonly used units of energy are calories or kilowatt-hours (kWh).

5.0Types of Energy:

There are different types of energy in the universe, each connected with different sources and physical phenomena. Some common types of energy are:

Kinetic Energy: KE is the energy of motion. Any moving object, whether it's a car, a flying bird, or even a flowing river, possesses kinetic energy. The kinetic energy an object possesses depends directly on its mass(m) and velocity(v). The kinetic energy can expressed in terms of the following:

$K E = \frac{1}{2} m v^{2}$

Potential Energy: Potential energy (PE) is energy that is stored. It relies on the object's position or configuration. The most familiar one is gravitational potential energy, which relies on the height of an object above the ground. The potential energy formula can be expressed as:

$PE = m g h$

The Sum of both potential (PE) and kinetic energy (KE) is known as mechanical energy.

Solar Energy: It is a form of energy obtained from the light produced by the sun. Energy is a widely used form of energy due to its easy availability and unlimited source. This energy from the sun is further divided into different types of solar energy, which include:
- Solar Thermal Energy: It is used to produce heat for water or air heating and electricity generation.
- Photovoltaic Energy: Photovoltaic energy directly converts sunlight into electricity with the help of solar cells.
- Concentrated Solar Power: This is a type of solar energy which utilises mirrors or lenses to concentrate sunlight to produce high-temperature steam for the production of electricity.
Electrical Energy: Electrical energy is usually produced by the flow of electrons in a conductor. It energises devices from small devices such as smartphones to huge systems such as citywide electrical grids.
Nuclear Energy: Nuclear energy is contained within the nucleus of atoms. It is released by nuclear reactions like fission (atom splitting) or fusion (atom combining). This energy is utilised in nuclear power plants and the sun.

6.0Energy Density

Energy density can be defined as the amount of energy that is stored in a unit of volume or weight, the more the energy density, the more the energy is stored in the object. This concept of energy plays an important role in understanding renewable and non-renewable sources of energy. Solar wind and windmills have a lower energy density in comparison to fossil fuels. The formula for energy density can be stated as:

$E n er g yDe n s i t y = \frac{E n er g y St ore d}{V o l u m eor ma ss}$

Practically, energy density has applications in various objects, including batteries, fuel, and storage systems, where the space and weight of the object are important.

7.0Law of Conservation of Energy

The law of conservation of energy is the most famous and important law related to energy, which specifically states that “Energy can neither be created nor be destroyed and can only be converted from one form to another form”. In other words, the total amount of energy in any closed system remains constant over time. This law implies all types of energy irrespective of their source.

To understand this more clearly, imagine a pendulum in which potential energy is transferred to kinetic energy and vice versa. As the pendulum oscillates, the energy goes back and forth between these two forms, but the energy does not change. In real-life situations, some of the energy tends to be lost as heat due to friction, but the overall energy in the system is conserved.

8.0Solved Examples on Energy:

Problem: A pendulum with a bob of mass 0.5 kg is released from a height of 2 meters above its lowest point. Calculate the speed of the bob when it reaches the lowest point.

Solution: At the maximum height, the potential energy of the pendulum will be maximum, and the kinetic energy will be zero.

m = 0.5kg (mass of the bob)

g = 9.8 m/s² (acceleration due to gravity)

h = 2m

PE = mgh

PE = 0.59.82=9.8J

Now, Using the law of conservation of energy:

PE_initial = PE_final

$9.8 J = \frac{1}{2} \times 0.5 \times v^{2}$

$v^{2} = \frac{19.6}{0.5} = 39.2$

$v = 39.2 \approx 6.26 m/s$

Problem 2: A ball is dropped from a height of 10 meters. After bouncing, it reaches a height of 6 meters. Assuming energy loss due to air resistance and ground friction, calculate the energy lost in the bounce.

Solution: Before the bounce,

The Potential energy of the ball at 10 meters = mgh

PE_Initial = mgh

$PE_{Initial} = 1 \times 9.8 \times 10 = 98 J$

After the bounce at 6 meters:

The final potential energy at 6m = mgh

$PE_{Final} = m g h$

$PE_{Final} = 1 \times 9.8 \times 6 = 58.8 J$

The energy lost during the bounce:

$PE_{Initial} - PE_{Final} = 98 - 58.8 = 39.2 J$

Problem 3: An electric motor lifts a 10 kg weight to a height of 12 meters in 5 seconds. What is the power required by the motor?

Solution: Given m = 10kg, h = 12m, t = 5seconds

To calculate the power, firstly, we would calculate the work done, which is the same as the energy used, by using the formula:

PE = mgh

$PE = 10 \times 9.8 \times 12$

PE = 1,176 J

The formula for power $P = \frac{E}{t}$

$P = \frac{1176}{5} = 235.2 W$

9.0Important topics in Class 10 Science: Energy

Renewable & non-renewable energy sources

10.0EUREKA by ALLEN – The Future of Class 10 Learning

With EUREKA by ALLEN, you're going to change the way you learn as a Class 10 student using an AI-based educational platform designed just for you! EUREKA offers everything from online videos, customized learning paths, immediate question resolution, and live statistics about how well you are doing with ALLEN's educational professional discipline combined with advanced technology for a more intelligent and effective learning experience!

Interactive concept-based learning Story-driven video lessons Board exam-oriented preparation Subjective answer writing practice Instant quizzes and performance feedback Real-time progress monitoring AI-powered doubt support available 24×7 NCERT & CBSE-aligned curriculum Flexible on-demand learning access

Explore Now

11.0Supporting Study Materials

This study material, focusing on Energy Sources and Environmental Engineering, is structured according to the latest NCERT guidelines. Complete with step-by-step energy conversion paths, biogas digester cross-sections, and high-yield subjective questions, this guide ensures absolute confidence for your school assessments and board examinations.

CBSE Class 10 Science Notes Chapter 13 Our Environment	NCERT Solution Class 10 Science Chapter 13: Our Environment

30-Second Quick Review: Sources of Energy

✔ A good source of energy should have a high calorific value and cause minimum pollution.

✔ Renewable sources can be naturally replenished.

✔ Coal, petroleum, and natural gas are non-renewable resources.

✔ Solar energy is clean, renewable, and sustainable.

✔ Wind energy converts the kinetic energy of moving air into electricity.

✔ Hydroelectric power uses the potential energy of stored water.

✔ Biomass is obtained from plant and animal waste.

✔ Biogas is mainly composed of methane.

✔ Nuclear energy is obtained through nuclear fission.

✔ Fossil fuels contribute to global warming and air pollution.

✔ Renewable energy helps conserve natural resources and reduce environmental damage.

12.0Previous Year Questions (PYQs) on Sources of Energy

Q1. What are the qualities of an ideal source of energy? (CBSE Board)

Answer: Qualities of an Ideal Source of Energy: An excellent, highly efficient fuel source must satisfy the following criteria:

High Calorific Value: It must yield a large amount of usable heat energy per unit mass or volume.
Low Pollution: It should not emit toxic gases, thick smoke, or leave behind large amounts of ash upon combustion.
Economic & Accessible: It must be easy to locate, extract, and transport safely without massive infrastructure costs.
Controlled Combustion: It should burn at a steady, manageable rate rather than causing an uncontrolled explosion.

13.0Recommended Next Topics

Electricity
Magnetic Effects of Electric Current
Human Eye and the Colourful World
Chemical Reactions and Equations

Frequently Asked Questions

What is the law of conservation of energy?

How is energy connected with work?

What is the energy efficiency of a system?

What is the definition of Energy?

Frequently Asked Questions

What is the law of conservation of energy?

How is energy connected with work?

What is the energy efficiency of a system?

What is the definition of Energy?

Join ALLEN!

Sources of Energy

1.0Master Fuel Dynamics, Power Generation, and Renewable Alternatives in Minutes

2.0Learning Outcomes

3.0Introduction to Sources of Energy

4.0What is Energy?

5.0Types of Energy:

6.0Energy Density

7.0Law of Conservation of Energy

8.0Solved Examples on Energy:

9.0Important topics in Class 10 Science: Energy

10.0EUREKA by ALLEN – The Future of Class 10 Learning

11.0Supporting Study Materials

30-Second Quick Review: Sources of Energy

12.0Previous Year Questions (PYQs) on Sources of Energy

13.0Recommended Next Topics

Table of Contents

Join ALLEN!

Sources of Energy

1.0Master Fuel Dynamics, Power Generation, and Renewable Alternatives in Minutes

2.0Learning Outcomes

3.0Introduction to Sources of Energy

4.0What is Energy?

5.0Types of Energy:

6.0Energy Density

7.0Law of Conservation of Energy

8.0Solved Examples on Energy:

9.0Important topics in Class 10 Science: Energy

10.0EUREKA by ALLEN – The Future of Class 10 Learning

11.0Supporting Study Materials

30-Second Quick Review: Sources of Energy

12.0Previous Year Questions (PYQs) on Sources of Energy

13.0Recommended Next Topics

Table of Contents