The electromagnetism It is a branch of physics that approaches from a unifying theory the fields of both electricity and magnetism, to formulate one of the four fundamental forces of the universe known so far: electromagnetism. The other fundamental forces (or fundamental interactions) are gravity and strong and weak nuclear interactions.
That of electromagnetism is a field theory, that is, based on physical magnitudes vector or tensor, which depend on the position in space and time. It is based on four vector differential equations (formulated by Michael Faraday and developed for the first time by James Clerk Maxwell, which is why they were baptized as Maxwell equations) that allow the joint study of electric and magnetic fields, as well as electric current, electric polarization and magnetic polarization.
On the other hand, electromagnetism is a macroscopic theory. This means that it studies large electromagnetic phenomena, applicable to large numbers of particles and considerable distances, since at the atomic and molecular levels it gives way to another discipline, known as quantum mechanics.
Even so, after the quantum revolution of the 20th century, the search for a quantum theory of electromagnetic interaction was undertaken, thus giving rise to quantum electrodynamics.
Electromagnetism application areas
This field of physics has been key in the development of numerous disciplines and technologies, in particular engineering and electronics, as well as the storage of electricity and even its use in areas of health, aeronautics or construction. urban.
The so-called Second Industrial Revolution or Technological Revolution would not have been possible without the conquest of electricity and electromagnetism.
Examples of applications of electromagnetism
- Stamps. The mechanism of these everyday gadgets involves the circulation of an electrical charge through an electromagnet, whose magnetic field attracts a tiny metal hammer towards a bell, interrupting the circuit and allowing it to start again, so the hammer hits it repeatedly and produces the sound that catches our attention.
- Magnetic suspension trains. Instead of rolling on rails like conventional trains, this ultra-technological train model is held in magnetic levitation thanks to powerful electromagnets installed in its lower part. Thus, the electrical repulsion between the magnets and the metal of the platform on which the train runs keeps the weight of the vehicle in the air.
- Electric transformers. A transformer, those cylindrical devices that in some countries we see on power lines, serve to control (increase or decrease) the voltage of an alternating current. They do this through coils arranged around an iron core, whose electromagnetic fields allow the intensity of the outgoing current to be modulated.
- Electric motors. Electric motors are electrical machines that, by rotating around an axis, transform electrical energy into mechanical energy. This energy is what generates the movement of the mobile. Its operation is based on the electromagnetic forces of attraction and repulsion between a magnet and a coil through which an electric current circulates.
- Dynamos. These devices are used to take advantage of the rotation of the wheels of a vehicle, such as a car, to rotate a magnet and produce a magnetic field that feeds alternating current to the coils.
- Telephone. The magic behind this everyday device is none other than the ability to convert sound waves (such as voice) into modulations of an electromagnetic field that can be transmitted, initially by a cable, to a receiver at the other end that is capable of pouring the process and recover electromagnetically contained sound waves.
- Microwave ovens. These appliances operate from the generation and concentration of electromagnetic waves on food. These waves are similar to those used for radio communication, but with a high frequency that rotates the diplodes (magnetic particles) of the food at very high speeds, as they try to align themselves with the resulting magnetic field. This movement is what generates the heat.
- Magnetic resonance imaging (MRI). This medical application of electromagnetism has been an unprecedented advance in health matters, since it allows to examine in a non-invasive way the interior of the body of living beings, from the electromagnetic manipulation of the hydrogen atoms contained in it, to generate a field interpretable by specialized computers.
- Microphones These devices so common today operate thanks to a diaphragm attracted by an electromagnet, whose sensitivity to sound waves allows them to be translated into an electrical signal. This can then be transmitted and decrypted remotely, or even stored and reproduced later.
- Mass spectrometers. It is a device that allows the composition of certain chemical compounds to be analyzed with great precision, starting from the magnetic separation of the atoms that compose them, by means of their ionization and reading by a specialized computer.
- Oscilloscopes. Electronic instruments whose purpose is to graphically represent the electrical signals varying in time, coming from a specific source. To do this, they use a coordinate axis on the screen whose lines are the product of the measurement of the voltages from the determined electrical signal. They are used in medicine to measure the functions of the heart, brain, or other organs.
- Magnetic cards. This technology allows the existence of credit or debit cards, which have a magnetic tape polarized in a certain way, to encrypt information based on the orientation of its ferromagnetic particles. By introducing information into them, the designated devices polarize said particles in a specific way, so that said order can then be “read” to retrieve the information.
- Digital storage on magnetic tapes. Key in the world of computing and computers, it allows to store large amounts of information on magnetic disks whose particles are polarized in a specific way and can be deciphered by a computerized system. These disks can be removable, like pen drives or now defunct floppy disks, or they can be permanent and more complex, like hard drives.
- Magnetic drums. This data storage model, popular in the 1950s and 1960s, was one of the first forms of magnetic data storage. It is a hollow metal cylinder that rotates at high speeds, surrounded by a magnetic material (iron oxide) in which the information is printed by means of a coded polarization system. Unlike the discs, it did not have a reading head and that allowed it a certain agility in the retrieval of information.
- Bicycle lights. The lights built into the front of the bicycles, which turn on when moving, operate thanks to the rotation of the wheel to which a magnet is attached, the rotation of which produces a magnetic field and therefore a modest source of alternating electricity. This electrical charge is then conducted to the bulb and translated into light.