Energy is ... Potential and kinetic energy. What is energy in physics?

Energy is what makes life possible not only on our planet, but also in the universe. However, it can be very different. So, heat, sound, light, electricity, microwaves, calories represent different types of energy. For all the processes taking place around us, this substance is needed. Most of the energy in the world receives everything from the Sun, but there are other sources of it. The sun passes it to our planet as much as would produce 100 million of the most powerful power stations at the same time.

What is energy?

In the theory put forward by Albert Einstein, the interrelation of matter and energy is studied. This great scientist was able to prove the ability of one substance to turn into another. It was found out, that energy is the most important factor of existence of bodies, and matter is secondary.

Energy - is, by and large, the ability to perform some kind of work. It is she who stands for the concept of force, capable of moving the body or giving it new properties. What does the term "energy" mean? Physics is a fundamental science, which many scientists of different epochs and countries devoted their lives to. Aristotle used the word "energy" to refer to human activity. In translation from the Greek language, "energy" is "activity", "power", "action", "power". The first time this word appeared in the treatise of the scientist-Greek under the name "Physics".

In the generally accepted sense this term was introduced into use by the English physicist Thomas Jung. This significant event occurred in the distant 1807. In the fifties of the XIX century. English mechanic William Thomson first used the concept of "kinetic energy", and in 1853 the Scottish physicist William Renkin introduced the term "potential energy".

Today, this scalar quantity is present in all sections of physics. It is a single measure of the various forms of motion and interaction of matter. In other words, it is a measure of the transformation of one form into another.

Units and symbols

The amount of energy is measured in joules (J). This special unit, depending on the type of energy, can have different designations, for example:

• W is the total energy of the system.
• Q is thermal.
• U is a potential.

Types of energy

In nature, there are many different types of energy. The main ones are:

• Mechanical;
• Electromagnetic;
• Electric;
• Chemical;
• Thermal;
• Nuclear (atomic).

There are other types of energy: light, sound, magnetic. In recent years, an increasing number of physicists are inclined to the hypothesis of the existence of so-called "dark" energy. Each of the previously listed species of this substance has its own characteristics. For example, the energy of sound can be transmitted by waves. They contribute to the vibration of the eardrums in the ear of people and animals, thanks to which you can hear sounds. In the course of various chemical reactions, the energy necessary for the vital activity of all organisms is released. Any fuel, food, batteries, batteries are the storehouse of this energy.

Our luminary gives the Earth energy in the form of electromagnetic waves. Only in this way can it overcome the expanses of the Cosmos. Thanks to modern technologies, such as solar panels, we can use it with the greatest effect. Excess of unused energy is accumulated in special energy storage facilities. Along with the above types of energy, thermal springs, rivers, tides and ebbs of the ocean, biofuel are often used.

Mechanical energy

This kind of energy is studied in the physics section, called "Mechanics." It is designated by the letter E. Its measurement is carried out in joules (J). What is this energy? Physics of mechanics studies the motion of bodies and their interaction with each other or with external fields. In this case, the energy due to the motion of bodies is called the kinetic energy (denoted by Ek), and the energy due to the interaction of bodies or external fields is called the potential energy (En). The sum of motion and interaction is the total mechanical energy of the system.

There is a general rule for calculating both types. To determine the amount of energy, calculate the work necessary to transfer the body from the zero state to this state. At the same time, the more work, the more energy the body will have in this state.

Separation of species by different characters

There are several types of energy sharing. According to various signs, it is divided into: external (kinetic and potential) and internal (mechanical, thermal, electromagnetic, nuclear, gravitational). Electromagnetic energy, in turn, is divided into magnetic and electrical, and nuclear energy is divided into weak and strong interactions.

Kinetic

Any moving bodies are distinguished by the presence of kinetic energy. It is often called driving. The energy of the body that moves is lost when it slows down. Thus, the faster the speed, the greater the kinetic energy.

When the moving body is in contact with a stationary object, the latter is transferred to the kinetic part, which leads to movement. The kinetic energy formula is as follows:

• E _to = Mv ^2: 2,
  Where m is the mass of the body, v is the speed of motion of the body.

In words, this formula can be expressed as follows: the kinetic energy of the object is equal to half the product of its mass per square of its velocity.

Potential

This kind of energy has bodies that are in some force field. So, the magnetic arises when the object is under the influence of a magnetic field. All bodies on earth have potential gravitational energy.

Depending on the properties of the objects of study, they can have different types of potential energy. So, elastic and elastic bodies that are capable of stretching have potential energy of elasticity or tension. Any falling body that was previously motionless, loses potential and acquires kinetic. In this case, the magnitude of these two species will be equivalent. In the gravitational field of our planet, the potential energy formula will have the following form:

• E _n = mhg,
  Where m is the mass of the body; H is the height of the center of mass of the body above the zero level; G - acceleration of gravity.

In words, this formula can be expressed as follows: the potential energy of an object interacting with the Earth is equal to the product of its mass, the acceleration of gravity and the altitude on which it is located.

This scalar quantity is a characteristic of the energy reserve of a material point (body) located in a potential force field and going to acquire kinetic energy due to the work of field forces. Sometimes it is called the coordinate function, which is a term in the Lagrangian of the system (the Lagrange function of the dynamical system). This system describes their interaction.

Potential energy is equated to zero for a certain configuration of bodies located in space. The choice of configuration is determined by the convenience of further calculations and is called the "normalization of the potential energy."

Law of energy conservation

One of the most basic postulates of physics is the Law of conservation of energy. In accordance with it, energy does not arise from anywhere and does not disappear anywhere. It constantly passes from one form to another. In other words, only a change in energy occurs. So, for example, the chemical energy of the flashlight battery is converted into electric, and from it - into light and heat. Various household appliances turn electrical into light, heat or sound. Most often, the end result of the change is heat and light. After that, the energy goes into the surrounding space.

The law of energy can explain many physical phenomena. Scientists claim that the total volume of it in the universe is constantly unchanged. No one can create energy anew or destroy. Developing one of its types, people use the energy of fuel, falling water, the atom. At the same time, one of its forms turns into another.

In 1918, scientists were able to prove that the law of conservation of energy is a mathematical consequence of the translational symmetry of time - the value of the conjugate energy. In other words, energy is preserved because the laws of physics do not differ at different times.

Energy Features

Energy is the ability of the body to do work. In closed physical systems, it is maintained throughout the time (as long as the system is closed) and represents one of the three additive integrals of motion that preserve the magnitude during motion. These include: energy, momentum, momentum. Introduction of the concept of "energy" is advisable when the physical system is homogeneous in time.

Internal energy of bodies

It is the sum of the energies of molecular interactions and the thermal motions of the molecules that make up it. It can not be measured directly, since it is a single-valued function of the state of the system. Always, when the system is in a given state, its internal energy has its intrinsic value, regardless of the history of the system's existence. The change in internal energy during the transition from one physical state to another is always equal to the difference between its values in the final and initial states.

Internal energy of gas

In addition to solids, energy also has gases. It is the kinetic energy of the thermal (chaotic) motion of the particles of the system, which include atoms, molecules, electrons, and nuclei. The internal energy of an ideal gas (mathematical model of a gas) is the sum of the kinetic energies of its particles. This takes into account the number of degrees of freedom, which is the number of independent variables that determine the position of the molecule in space.

Use of energy

Every year, humanity consumes more and more energy. Most often, fossil fuels such as coal, oil and gas are used to generate the energy needed to illuminate and heat our homes, work vehicles and various mechanisms. They refer to non-renewable resources.

Unfortunately, only a small part of the energy is extracted on our planet with the help of renewable resources, such as water, wind and the Sun. To date, their share in the energy sector is only 5%. Another 3% of people receive in the form of nuclear energy produced at nuclear power plants.

Non-renewable resources have the following reserves (in joules):

• Nuclear energy - 2 x 10 ²⁴ ;
• Energy of gas and oil - 2 x 10 ²³ ;
• Internally the heat of the planet - 5 x 10 ²⁰ .

The annual value of renewable resources of the Earth:

• The energy of the Sun is 2 x 10 ²⁴ ;
• Wind - 6 x 10 ²¹ ;
• Rivers - 6.5 x 10 ¹⁹ ;
• Sea tides - 2.5 x 10 ²³ .

Only with the timely transition from the use of non-renewable energy resources of the Earth to renewable, humanity has a chance for a long and happy existence on our planet. To translate advanced developments, scientists around the world continue to carefully study the diverse properties of energy.