# Types of Energy

We use several types of energy on a daily basis. The most important are: mechanical energy, electrical energy, thermal energy, chemical energy, nuclear energy, light energy and sound energy.

Remember that energy is a concept used in several scientific areas, such as chemistry, physics and biology. It basically means the ability to produce heat or to do work. That is, when something is working, it has energy.

## What Is Mechanical Energy?

Mechanical energy, or total mechanical energy, differs from other types of energy in that it is responsible for propelling object movement. It has been defined as the ability of an object to perform work. When the ability to do work is related to movement, it is called kinetic energy. However, if the ability to do work is related to the position of an object, it is called potential energy.

### Kinetic Energy and Potential Energy

Kinetic energy is related to the mass and speed of a body. The equation for Kinetic Energy is:

• KE = 1/2 m v^2
• m is for mass, and v is for velocity

Thus, mechanical energy is produced by all types of machines and moving objects. For example, hydropower plant turbines convert the kinetic energy of falling water into mechanical energy. Then a generator converts the mechanical energy from the turbine into electrical energy.

To better understand the definition of potential energy, imagine two scenarios. In the first one, a block is suspended by a thread, so that if we cut it, the block will fall. During the fall movement, it will perform work. In the second case, the block is attached to a spring compressed by a wire. If the wire is cut, the block will be thrown forward, generating movement.

In both cases, the block will have the capacity to perform work, due to the energy stored by its position. This stored energy is potential energy and can be of two types:

1. Potential gravitational energy: when the energy originates from the Earth’s gravitational pull on an object.
2. Potential elastic energy: originates in the action that a spring can exert on an object.

## What Is Electrical Energy?

Electric energy is the working capacity of an electric current. It is generated by turbines or generators that transform chemical and mechanical energy into electrical energy. The production of electrical voltages between two points allows the establishment of electrical currents. It is one of the most used energy sources today. The electrical energy used in homes and businesses is generated in plants that transmit it through cables and towers to the end users. Distribution is made by public or private companies that install devices in residential areas to measure energy consumption and charge for the service.

It is produced mainly in hydroelectric plants, but can also be created by thermoelectric, nuclear and wind power plants. One of the advantages of this type of energy is that it can be transported very easily, through cables and wires, for example.

The International System of Units (SI) uses joule units to measure energy. However, kilowatt-hours (kWh) is the most widely used measure when it comes to energy consumption.

In the transmission lines that leave a hydroelectric plant, the energy is transported for many kilometers to the end users. On the way, it passes through transformers that reduce its voltage for use in the outlets. Electric energy is easily transformed into other types of energy. All electrical devices use this energy to generate light, heat, movement or sound.

## What Is Thermal Energy?

Thermal energy is a broad term, used to express different thermodynamics. For example, internal energy or an amount of heat exchanged between systems of different temperatures. In this article, we use the term thermal energy as a synonym for internal energy. This form of energy is the sum of the kinetic and potential energies of the atoms and molecules that constitute a thermodynamic system.

Thermal energy depends directly on the absolute temperature of the object. It is measured in kelvin (K), and also depends on the amount of degrees of freedom of the system. That is, the number of directions in which the molecules can move, vibrate, oscillate or even rotate.

According to the first law of thermodynamics, the thermal energy of a system can be converted into other forms of energy. For example, heat or work. Heat refers to the transfer of thermal energy, exclusively due to temperature difference between a system and its surroundings. Work, in turn, concerns the application of forces on the system or by the system.

Every day, we make use of many sources to produce thermal energy. The human body, for example, consumes a large amount of nutrients to generate the thermal energy necessary for the functioning of our vital organs. Much of the electrical energy produced in the world depends on the ability to transform thermal energy into electricity.

## What Is Chemical Energy?

Chemical energy is the product of chemical reactions between two or more substances. The energy that can be released (or absorbed) by a reaction between a set of chemicals is called internal energy.

In a battery, for example, acid interacts with metal, causing it to lose electrons and generate electricity. In a candle, paraffin is a fuel that undergoes a reaction and releases light and heat.

Chemical energy relates to thermodynamics. Internal energy is a property characteristic of a state of a thermodynamic system. The change in this system is equal to the heat absorbed minus the work done by the system. In thermodynamic chemistry, the term used for potential energy is chemical potential, and the Gibbs-Duhem equation is often used to measure chemical transformation.

## What Is Nuclear Energy?

Nuclear energy, also called atomic energy, is the result of the disintegration of the atoms of an element releasing energy. Thermonuclear plants, which use uranium and other elements as fuel, produce nuclear energy.

The operating principle of a nuclear power plant is the use of thermal energy (heat) to generate electricity. The heat comes from the fission of uranium atoms. This heat is used within a water heating system. This water, when transformed into steam, drives electricity generating turbines.

Uranium is a non-renewable mineral resource found in nature, which is also used in the production of radioactive material for use in medicine. In addition to its use for peaceful purposes, uranium can also be used in the production of weapons, such as the atomic bomb.

As a highly concentrated and high-yielding energy source, several countries use nuclear energy as an energy source. Nuclear plants already account for 16% of the electric energy produced in the world.

More than 90% of nuclear power plants are concentrated in the United States, Europe, Japan and Russia. In April 2018, the Russian government inaugurated the world’s first floating nuclear power plant, located in the Arctic Sea.

In some countries, like Sweden, Finland and Belgium, nuclear energy already represents more than 40% of the total electricity produced. South Korea, China, India, Argentina and Mexico also have nuclear power plants.

## What Is Light Energy?

Light energy is the energy that light waves generate and transport. When light travels it can act like an electromagnetic wave or like a particle, since it can interact with other matter. Those particles are called photons.

The lumen is the unit that measures the total quantity of visible light emitted by a source per unit of time. Luminous energy travels through waves and at the speed of light, therefore it cannot be stored.

The sun is the main source of light on Earth. It transmits a significant amount of light energy capable of sustaining the development of life on our planet. However, there are other sources of light energy, such as fire or lasers.

Similar to heat produced by thermal energy, some substances emit light. Light is the result of electromagnetic waves that may or may not be seen by the human eye. The ability to observe light depends on the length of its waves. Among other things, these electromagnetic waves are responsible for our perception of colors as well as plant photosynthesis.

## What Is Sound Energy?

Sound energy or acoustic energy is the amount of energy transmitted by sound waves. It is produced by the vibration of an object and moves through some physical medium (air, for example).

In this regard, sound energy encompasses different forms of energy, such as kinetic, potential and even thermal energy. From a physical point of view, sound is a set of particles that move or vibrate in a regular and organized way. They propagate in response to some specific stimulus that in turn gives them their initial form of energy.

Sound energy is not usually used to generate other forms of energy. This is because even the loudest sounds don’t have much energy in them. However, it is possible to measure this energy using Decibels and in some cases sound energy can move objects.

### The Propagation of Sound

Similar to light waves, sound waves are capable of propagating through different materials, be they liquid, solid or gaseous. However, they are unable to propagate in a vacuum, unlike electromagnetic waves.

Sounds are an important part of everyday activities. Sound energy is what makes music and speech possible, for example. It is not difficult to come up with examples of sound energy. Here we will detail some:

• During thunderstorms, intense thunder makes the window panes shake. It is the sound energy that is transmitted to the glass and is converted into kinetic energy (movement).
• Try placing your hand on the subwoofer. You will notice how the sound vibrations bounce off your hand. That way you can actually feel the music!
• The classic episode of a soprano singer shattering crystal goblets is a demonstration of the enormous sound energy that vocal cords can produce. Crystal is resonant enough to break at volumes that some people can produce without amplification. The frequency is so high that the crystal, picking up the sound waves, fractures because it vibrates so intensely.

## Renewable and Non-Renewable Energy

In addition to the types of energy mentioned above, many other types of energy are produced by renewable energy sources and non-renewable energy sources.

### Renewable Energy Sources

Renewable energy sources are natural resources considered inexhaustible and used for energy generation. Renewable energy sources have several advantages in their uses, as they minimally harm the environment, when compared to conventional energy sources.

Examples of renewable energy sources are solar energy (sunlight), wind energy, hydropower (water), tidal energy, geothermal energy and biomass as fuel.

### Non-Renewable Energy Sources

Non-renewable sources of energy are those that use exhaustible natural resources. That is, resources that will deplete, either in the near future, or in a medium or long term. The use of this type of energy source, presents environmental problems, as well as disputes involving the extraction and commercialization of raw materials.

The main examples of non-renewable energy sources are fossil fuels (oil, coal, natural gas and oil shale) and nuclear fuels.

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