# Electric power

We define electricity as the form of energy that results from the existence of a potential difference between two points. When these two points are put in contact by means of an electrical conductor we obtain an electric current.

In physics, the electric potential energy, also called electrostatic potential energy, is the potential energy of the electrostatic field. This is an energy that has an electrical charge distribution, and is linked to the force exerted by the field generated by the distribution itself. Together with magnetic energy, the electric potential energy constitutes the energy of the electromagnetic field.

The electrostatic potential energy can be defined as the work done to create a load distribution from an initial configuration in which each component of the distribution does not interact with the others. For example, for a discrete load system, it coincides with the work carried out to carry the individual loads from a position in which they have zero electric potential to their final disposal. The electrostatic potential energy can also be defined from the electrostatic field generated by the distribution itself, and in this case its expression is independent of the field source.

This is an amount that can be negative or positive, depending on whether the work carried out to bring it into the assumed configuration is positive or negative. Two interactive charges of the same sign have positive energy, since the work done to bring them closer must overcome their repulsion, while, for the same reason, two charges of the opposite sign have negative energy.

## Physical aspects of electric power

From the physical point of view, electrical energy is negative electric charges (electrons) that move through the electrical conductor, usually metallic, due to the potential difference between its ends. The reason why drivers of metallic origin are usually used is because they have more free electrons.

The electric charges that travel through the conductor are part of the atoms of the conductor's own substances.

In physics, the potential for electrical energy is also called electrostatic potential energy.

At a slightly more technical level of physics, the electric power potential is the potential energy of the electrostatic field. It is the energy that has an electrical charge distribution that is linked to the force exerted by the generated field of the same distribution. Along with magnetic energy, the potential for electrical energy is the energy of the electromagnetic field.

The electrostatic potential energy can be defined as the work done to create a load distribution from an initial configuration in which each component of the distribution does not interact with the other. The electrostatic potential energy can also be defined from the electrostatic field generated from the same distribution, and in this case its expression is independent of the field source.

It is a magnet that can be negative or positive, depending on whether the work done so that they are in the adopted configuration is positive or negative. Two charges that interact in the same sign have positive energy, since the work done to bring them closer must overcome their repulsion. For the same reason, two opposite charges have negative energy.

## Electric power generation

Electric power can hardly be found freely in nature in a way that can be exploited. It can be seen in thunderstorms but the difficulty of storing and controlling such an amount of energy makes them practically unusable.

There are several ways to generate electricity that we can classify as renewable or non-renewable. The ways to generate renewable electric power are those in which no fuel is used or the fuel is inexhaustible (solar energy, wind energy, hydroelectric energy, geothermal energy, etc.). On the other hand, the ways of generating non-renewable electricity require a fuel that, however abundant, tends to run out, such as nuclear energy, thermal energy (coal, oil, gas ...), etc.

## Use of electric power

Electrical energy can be transformed into many other types of energy such as mechanical energy (electric motors, machines ...), thermal energy (heaters, stoves ...) or light energy (light). The great advantage that electric power gives us is the ease of transporting it.

The use of electricity is very widespread in modern society and the current through the connection to the electricity grid or by batteries or accumulators: it is enough to think about the use of the lighting of buildings (public and private) and roads, in the power of appliances and equipment, as well as in industrial production processes or in electrical machines, such as electric motors.

Therefore, the discovery of electric power has represented a very strong technological, economic and social revolution. Its use has caused a strong and irreversible need due to its benefits compared to mechanical energy produced by thermal engines (combustion engines). Among them was the fact of being able to be transported at a distance, the low operating noise of electrical equipment, the absence of exhaust gases at the point of use and the smaller footprint of an electric machine.

Among the disadvantages only the fact of not being a primary source. The use of electric power implies the need for a conversion infrastructure that inevitably introduces a loss of efficiency in the conversion process and upstream in transportation along power lines.

## Power plants

Electricity, with the exception of lightning atmospheric electricity and the weakly negative potential of the Earth, is not a primary energy source of the earth, so it has to be produced by transforming an energy source primary. In this way, electric power is considered as a secondary energy source. In the process of transformation, performance always less than 100%, occurs within the power plants.

In all electric power production plants, with the exception of photovoltaic solar energy, three elements are needed to produce electricity:

• Turbine
• Alternator
• Transformer

Another important element to produce electricity is water in liquid form (as in hydroelectric power plants) or in the form of high pressure steam (in thermal power plants, geothermal power plants, in nuclear fission and in solar thermal power plants) , in order to turn the turbines to produce in a more constant way possible alternating current by means of the alternator.

The use of water presents the following problems derived from the need to heat it:

• Water availability.
• Thermal pollution of water, if not recovered, is dispersed in the atmosphere in the form of water vapor or fed back into lakes, rivers and the sea.

In the case of wind plants, water is not needed, since the turbines are driven by the force of the wind.

### Transport and distribution of electrical energy

Once electricity production is finished, there is a need to transport it on a large scale. The large-scale transport and distribution of electricity produced by the plants to the end users is carried out through the transmission network and the distribution network.

## Joule's Law

The Joule's law, in fact, are two different laws, which associate the heat generated by the electric current and the dependence of the internal energy of an ideal gas with respect to its pressure, volume and temperature.

Joule's first law (also known as the Joule effect) is a physical law that establishes the relationship between the electric current that passes through a conductor and the heat it generates. The name is dedicated to James Prescott Joule, who worked on this concept in the 1840s and expresses it in the following way:
Q = I2 · R · t

In the formula Q is the heat generated by the constant current I, which passes over a conductor t with resistance R in time. When the current (measured in amperes), the resistance (measured in ohms) and the time (measured in seconds), the unit of Q will be joules.

Joule's first law is also sometimes known as the Joule-Lenz law, because he was later found independent by Heinrich Lenz.

Joule's second law means that the internal energy of an ideal gas depends solely on its temperature, regardless of its volume and pressure.

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Last review: November 25, 2016

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