What Is Energy?
Energy is the ability of matter to produce work in the form of movement, light, heat, etc. Energy is a scalar physical quantity and can come in many forms.
Energy is a unique measure of various forms of movement and interaction of matter, a measure of the transition of matter from one form to another. The introduction of the concept of energy is important because if the physical system is closed, then its energy is stored in this system during the time during which the system will be closed.
Energy is usually denoted by the symbol E. To indicate the amount of heat (the amount of energy transmitted by heat transfer), the symbol Q is generally used. To designate work as the amount of energy transferred, generally the symbol W is used. The symbol U is generally used to indicate the internal energy of the body (the origin of the symbol must be specified).
The electric field is the field generated by an electrically charged object. This field generates a force that acts on other objects also electrically charged.
"Energy is neither created nor destroyed": the law of conservation of energy.
The law of conservation of energy announces that: "energy is neither created nor destroyed" , it can only be transformed. It is only possible to convert one type of energy into another type of energy.
A closed system is a system that does not exchange energy with the outside. Therefore, in a closed system the total amount of energy always remains constant.
For example, nuclear energy into electrical energy is a clear example of energy transformation. Electric energy is not created, but it is a transformation from nuclear energy to electricity.
What are the types of energy?
There are different ways to classify different types of energy. The main types of energy are as follows:
- Nuclear. It is obtained from the nuclei of the atoms.
- Mechanics. It can be potential and kinetic. It depends on the position and speed of a body.
- Thermodynamics . This type refers to the internal energy of a thermodynamic system.
- Electromagnetic . Electromagnetic energy is derived from the electromagnetic nature of matter.
- Electric . Related to the movement of electrons in a conductor.
- Magnetic . Magnetic energy is the energy that is generated in a magnetic field.
- Sonora . Sound energy is related to sound and its propagation by waves.
- Chemistry . It is stored in the bonds of chemical compounds.
Energy can be presented in various forms, which, due to the principle of conservation of energy, can be transformed into each other. Therefore, we can talk about different types of energy more depending on their effects than their natural origin.
What does nuclear energy consist of?
The mass of an atomic nucleus is less than the sum of the masses of the elementary particles that make it up (mass defect). This mass defect is due to the appearance of a cohesion energy absorbed by the nuclear structure and which can be calculated using Einstein's theory of relativity.
This energy can be released in the form of radiant energy and kinetic energy from the particles that are expelled from the nucleus.
What is mechanical energy?
Mechanical energy is due to the geometric and dynamic variables of the system, from a macroscopic point of view, and is the one that responds to the simplest mathematical scheme.
The definition of mechanical energy in a material body of constant mass (m) is the sum of its kinetic energy and its potential energy. The kinetic energy is proportional to the speed of the body while the potential energy depends on the position of the body in the field of forces that surrounds it.
Thus in the case of free fall the position would be determined by the height and the force field by the force of gravity. One can also consider the potential energy of deformation due to the elastic properties of a deformed body such as a compressed spring.
What does thermodynamic energy consist of?
The definition of thermodynamic energy makes sense from a molecular point of view. Taking into account the thermodynamic variables, we can define the internal energy U of a system as the sum of the kinetic energies of the molecules that compose it and the potential energy of the forces between them.
Each one of the atoms or molecules of a body or of a substance are in continuous movement, either in rotation, translation or vibration, with respect to the equilibrium position, more or less intense depending on the temperature. From this point of view we can say that thermal energy is equivalent to the kinetic energy of molecules, as formulated by L. Boltzmann in his kinetic theory of gases.
Internal energy is not an absolutely measurable quantity, but only the energy variations between two states of the system are measured (first principle of thermodynamics).
The name given to it depends on the manifestation of this energy or on the nature of the phenomenon that generates it. We define
- bond energy or formation energy the difference between the energy of a molecule and that of the atoms that form it (bond),
- dissociation energy the energy released in the dissociation of a compound,
- activation energy the increase in energy required for a chemical reaction to occur (activation energy) and
- resonance energy the difference between the theoretical formation energy and the actual formation energy of a resonant compound (resonance).
Free energy relates the variation of internal energy (U) or enthalpy (H) with the variation of entropy (S) of a system and serves to indicate in which direction the system will evolve spontaneously (affinity).
What is electromagnetic energy?
Definition of electromagnetic energy: it is the energy derived from the electromagnetic nature of matter.
Electromagnetic energy manifests itself basically in two ways: transforming itself into kinetic energy from the electrical charges that are in its zone of influence-which can be converted into heat (Joule effect) or mechanical energy (electric motors) - or spreading as radiant energy out of the medium where it has been generated in the form of electromagnetic waves-which can then be converted into light energy, etc. - or also, on an atomic scale, emitting particles carrying a certain amount of energy determined by the Planck equation (photoelectric effect).
What do renewable energy and non-renewable energy mean?
There are also two definitions of energy that refer to the form of use. In this sense we can distinguish:
- renewable energy
- non-renewable energy
We usually refer to these two definitions to talk about the generation of electrical energy, but the use of these types of energy is not always to generate electricity.
Non-renewable energy is energy that comes from limited sources. In non-renewable, the consumption of this type of energy is greater than its regeneration capacity. Some examples of this type of energy are fossil fuels (coal, oil and natural gas) and nuclear energy, among others.
In the case of nuclear energy, and more specifically with nuclear fission, although a large amount of energy can be obtained per unit of nuclear fuel, uranium is a limited natural resource that does not regenerate itself.
How is it used? Most common uses and applications
The use of energy as a source of work has always been an essential necessity for man and one of the fundamental factors of modern economic development and technical progress.
Until the beginning of the industrial revolution, except for isolated experiments, man used as energy sources, muscular force, hydraulic energy and wind energy for the production of mechanical work, and vegetable fuels for obtaining heat.
Until then, these were the only resources used to obtain energy, although in time these systems were perfected to achieve higher yields (more rational use of animals, improvement of sailing techniques, invention of the hydraulic wheel, etc.).
Today, the most widely used energy sources are waterfalls, fossil fuels, and nuclear fission. Less importantly, solar, wind, geothermal and tidal energy appear.
The exploitation of hydraulic energy requires adequate topographic and hydrographic conditions and the construction of reservoir works and large machinery in order to achieve acceptable energy yields (which can reach 80%, or more, of the potential energy of the Water). Generally always for the production of electrical energy.
Steam engine and thermal engines
The beginning of development for energy exploitation techniques was in the appearance of the steam engine and the transformation of the hydraulic wheel into a turbine.
The most important source of energy is fossil fuels, which have undergone exponential growth in recent years. The maximum performance is much lower than that obtained by hydraulic energy, but its high energy concentration explains the considerable development it has undergone.
The third type of energy most used is nuclear energy , which is generally obtained by fission of the nuclei of substances such as uranium, plutonium, thorium, etc ... The technology of nuclear fusion reactions is not yet sufficiently developed to allow industrial exploitation and is used only in experimental laboratories and military applications.
The energy obtained in nuclear fission is manifested in the form of heat, and reaches temperatures much higher than those obtained with conventional fuels, however, the yields that can currently be obtained are still very low (of the order of 30% ).
Nuclear energy has application basically in the production of electrical energy and in the propulsion of ships. The electrical energy obtained with this system (nuclear power plant) has a reasonable cost only in the case of large reactors, which provide very high powers.
History of the study of energy
The notion of energy appears for the first time from the investigations of Joule and Carnot on the conversion of heat into mechanical work and thanks to the Helmholtz theory in which it links the work done by an isothermal system with internal energy and entropy of this system. In this way, energy is not only linked to the concept of mechanical work, but also to electrical, chemical or calorific work. For this reason we can speak of electrical energy, chemical energy and heat energy.
At the same time, it can be said that if a certain amount of work disappears in an isolated physical system, or an equivalent part of this work, being part of different forms of energy, the same amount of work must appear under other energy forms according to the definition of energy conservation law.
As a result of the investigations carried out by William Thomson and RJE Clausius in the middle of the s. XIX, the process of energy degradation was revealed, that is, that the useful work that can be obtained in an isolated system not all energy is conserved but there is a part of this energy that is degraded (entropy, second thermodynamic principle).
Later, following the theory of A. Einstein on the equivalence between mass and energy (1905), the conservation principle was expanded, and currently there is no difference between conservation of mass and conservation of energy, giving rise to the theory of relativity, conservation law.
In 1900, Max Planck explained many phenomena hitherto unexplained through the theory of energy quanta (quantum mechanics), which made the contribution a fundamental concept for the knowledge of energy.
Last review: March 15, 2020