Physics

# Energy

The capacity of working of an object is called energy. It may exist in kinetic, thermal, electrical, chemical, nuclear, or other various forms. Like work, energy is also a scalar quantity. Actually work is done by energy transfer. There are always two factors involved in doing work – one who does the work and the one on whom the work is done. The energy of the object doing work decreases as much as the energy of the other object increases. The entire energy of the system remains constant. The work done is equal to the energy transferred. ## Conversion of Energy: Energy is not destroyed only it is transformed. 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.” According to this law, the total amount of energy in the universe is always constant. .
For example, when a body falls from a height, its gravitational potential energy decreases but the velocity of the body increases. Due to this the kinetic energy of the body increases as much as the potential energy decreases. That is, while falling from a height, the total energy in each position of the body remains constant.

### Various Examples of Energy conversion

#### 1. Conversion of Electrical Energy into Light Energy

Light energy is produced when an electric bulb is lit. The input to the bulb is electricity and it converts it into light and heat energy.

#### 2. Conversion of Electrical Energy into Thermal Energy:

In an electric heater, electrical energy is converted into thermal energy. The heating element of an electric heater is simply an electrical resistor, which converts electrical energy into thermal energy.

#### 3. Conversion of Kinetic Energy into Electrical Energy

In the dynamo, electric generator, different types of turbines, etc. the kinetic energy of the coil is converted into electrical energy.

#### 4. Conversion of Sound Energy into Electrical Energy

In the microphone, the conversion of sound energy into electrical energy takes place. Through the principle of electromagnetic induction, the vibrations created by noise can be converted into electrical energy

#### 5. Conversion of Electrical Energy into Sound Energy

The electrical energy coming from the microphone by loudspeakers is converted into sound energy. A loudspeaker works by sending an electric current through a coil of wire to produce a magnetic field. So that it moves back and forth with the changing in electric current. This coil is connected to a lightweight paper membrane, which vibrates and produces sound.

#### 6. Conversion of Chemical Energy into Light and Thermal Energy

When a candle or any other object is lit, chemical energy is converted into light and heat energy.

#### 7. Conversion of Potential Energy into Kinetic Energy

By pouring the accumulated water from the dam built on the rivers and spinning it on the turbine, the potential energy is converted into kinetic energy.

#### 8. Conversion of Kinetic Energy into Potential Energy

When a bullet released from a gun hits a target, its kinetic energy is converted into potential energy.

#### 9. Conversion of Nuclear Energy into Electrical Energy

In nuclear reactors, the nuclear energy of an atom is converted into electrical energy.

#### 10. Conversion of Nuclear Energy into Heat, Light, and Mechanical Energy

Nuclear energy is converted into heat, light, and mechanical energy in the atomic bombs, hydrogen bombs Sun, and other stars. ### Mass-Energy Equation

In 1905, the scientist Einstein said that every substance has energy due to its mass. Whenever there is a loss of mass we get energy. Mass can be converted into energy and energy into mass.

According to Einstein’s mass-energy equation, the total energy produced, (E) = mc2 when an object of mass m is completely converted into energy.
where c = 3 × 108 m/s (speed of light) ### Important Questions

Question 1: What is the law of conservation of energy?

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.” According to this law, the total amount of energy in the universe is always constant.

Question 2: What is the relation between energy and work?

Work is done by energy transfer. There are always two factors involved in doing work – one who does the work and the one on whom the work is done. The energy of the object doing work decreases as much as the energy of the other object increases.

Question 3: How does electric energy convert into light energy?

An electric bulb converts electric energy into light and heat energy.

Question 4: What is the conversion process of electric energy into sound energy?

A loudspeaker works by sending an electric current through a coil of wire to produce a magnetic field. So that it moves back and forth with the changing in electric current. This coil is connected to a lightweight paper membrane, which vibrates and produces sound.

Question 5: How does kinetic energy convert into electric energy?

In the dynamo, electric generator, different types of turbines, etc. the kinetic energy of the coil is converted into electrical energy.

Question 6: Give examples of conversion of electrical energy into thermal energy.

In an electric heater, electrical energy is converted into thermal energy. The heating element of an electric heater is simply an electrical resistor, which converts electrical energy into thermal energy.

Question 7: Give examples of conversion of potential energy into kinetic energy?

When a body falls from a height, its gravitational potential energy decreases but the kinetic energy of the body increases. In this way, potential energy converts into kinetic energy.

Question 8: Give examples of conversion of kinetic energy into potential energy?

When a bullet released from a gun hits a target, its kinetic energy is converted into potential energy.

Question 9: Give examples of the conversion of nuclear energy into heat, light, and mechanical energy?

Nuclear energy is converted into heat, light, and mechanical energy in the atomic bombs, hydrogen bombs,s and Sun and other stars.

Question 10: What is Mass-Energy Equation?

In 1905, the scientist Einstein said that every substance has energy due to its mass. Whenever there is a loss of mass we get energy. Mass can be converted into energy and energy into mass.

According to Einstein’s mass-energy equation, the total energy produced, (E) = mc2 when an object of mass m is completely converted into energy.
where c = 3 × 108 m/s (speed of light)

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