In physics, the energy of the electromagnetic field is the energy stored in a certain region of space by the electromagnetic field, and is formed by the sum of the energies associated with the electric field and the magnetic field.
This definition also includes special cases of pure electric and pure magnetic fields.
In electromagnetic waves these two quantities are always equal and it is convenient to speak of the flow of energy transported by the wave in the unit of time, through a surface, by using the Poynting vector.
Electromagnetic energy also includes the energy of electromagnetic waves; for this reason, it is also called radiant energy.
What Is an Electromagnetic Wave?
Electromagnetic waves are a consequence of the vibrations produced between magnetic and electric fields. They are also formed by oscillating electric and magnetic fields.
Electromagnetic waves propagate through space with an electric and magnetic component. The electric and magnetic fields of a wave are perpendicular to each other and to the direction of the wave. These components oscillate at right angles to each other and to the direction of wave propagation.
The set of electromagnetic waves that travel at a constant velocity of 3.00 x 10 8 m/s through matter or in a vacuum is called electromagnetic radiation. Electric and magnetic fields cannot deviate their trajectory but they can show interference.
Types of Electromagnetic Energy
There are different types of electromagnetic energy. Electromagnetic waves are classified depending on their frequency and wavelength, that is, their electromagnetic spectrum. According to this classification there are the following types of electromagnetic energy:
gamma radiation.
Ultraviolet rays.
X-rays.
infrared rays.
Microwave and radio waves.
Light energy that comes from the spectrum of light visible to the human eye.
Examples of Electromagnetic Energy
Electromagnetic energy manifests itself through many energy sources. Some of them are natural, such as solar radiation, and others are of artificial origin, such as microwave ovens.
Here are some examples where electromagnetic energy is manifested:
Magnetic Suspension Trains:
These types of trains are levitating trains that are sustained thanks to the force exerted by powerful electromagnets. When these electromagnets are powered by an electric current, the intensity of the magnetic field increases, generating a repulsive force between the wagons and the metal rail.
Electric Transformers
Electrical transformers are devices that allow the voltage of an electrical current to be varied. It is based on two coils (the primary and the secondary) made up of a conductive wire wound around an iron core.
When alternating current enters the primary coil it generates a magnetic field that activates the secondary coil. The magnetic field received by the second coil generates an electrical output current.
If the number of turns of the wire is different between the primary and secondary coil, the output voltage is different.
Electrical transformers are used to adapt high voltage current to the voltage used in our homes, for example.
Electric Motors
Motors are devices capable of transforming electrical energy into mechanical energy, that is, into a movement. During this process, electricity is transformed into electromagnetic energy by the rotor and stator.
The rotor, which is the moving part, is formed by coils located between the poles of a permanent magnet located in the stator. The generated electromagnetic field keeps the rotor turning at a constant speed.
Electric Generators
These types of devices work on the same principle as electric motors but in the opposite direction. In this case, the generator receives mechanical work that turns the rotor, generating an electromagnetic field from which electricity is obtained.
Microwaves:
Microwave ovens can heat food from the generation and concentration of electromagnetic waves. These waves are similar to those that allow radio communications.
However, in this case they have a higher frequency that transforms the food dipoles at very high speeds. The movement of these particles generates the kinetic energy that heats the food.
Magnetic Resonance Imaging
Magnetic resonance imaging is an application of nuclear medicine to non-invasively examine the patient. The obtaining of these images that are used for the diagnosis of diseases are generated through the emission of waves with electromagnetic energy.
Basic Concepts
In addition to electromagnetic waves, it is necessary to know some basic aspects related to
Electric Charge
Electric charge is the amount of electrical energy that a particle or object carries, and it is a physical quantity that determines how much the presence of an electromagnetic field affects it.
Electric Current
An electric current is generated by the movement of electric charges. There are two types of basic electrical charges: electrons that have a negative charge and protons that have a positive charge.
Magnetism
Magnetism is a repulsive or attractive force exerted by electrically charged particles on each other.
Electromagnetic Field
The electromagnetic field is caused by elements that have an electric charge that affect the behavior of other charged particles in the set of electric and magnetic fields.
