The electromagnetic induction is defined as the induction of an electromotive force (voltage) in a medium or near body because of the presence of a changing magnetic field. This phenomenon was discovered by the British physicist and chemist Michael Faraday, in the course of the year 1831, through Faraday's law of electromagnetic induction.
Faraday carried out experimental tests with a permanent magnet surrounded by a coil of wire and observed the induction of a voltage on said coil, and the circulation of an underlying current.
Michael Faraday
This law states that the induced voltage on a closed loop is directly proportional to the rate of change of the magnetic flux as it passes through a surface, with respect to time. Thus, it is feasible to induce the presence of a voltage difference (voltage) on an adjacent body due to the influence of varying magnetic fields.
In turn, this induced voltage gives rise to the circulation of a current corresponding to the induced voltage and the impedance of the object of analysis. This phenomenon is the principle of action of power systems and devices of daily use, such as: motors, generators and electrical transformers, induction furnaces, inductors, batteries, etc.
Formula and units
The electromagnetic induction observed by Faraday was shared with the world of science through mathematical modeling that allows replicating this type of phenomena and predicting their behavior.
Formula
To calculate the electrical parameters (voltage, current) associated with the phenomenon of electromagnetic induction, first it is necessary to define what is the value of magnetic induction, currently known as the magnetic field.
To know what is the magnetic flux that passes through a certain surface, then the product of magnetic induction by said area must be calculated. So:
Where:
Φ: Magnetic flux
B: Magnetic induction
S: Surface
Faraday's Law indicates that the electromotive force that is induced on neighboring bodies is given by the rate of change of the magnetic flux with respect to time, as detailed below:
Where:
ε: Electromotive force
By substituting the value of the magnetic flux in the previous expression, we have the following:
If integrals are applied to both sides of the equation in order to delimit a finite path for the area associated with the magnetic flux, a more precise approximation of the required calculation is obtained.
Furthermore, the calculation of the electromotive force in a closed circuit is also limited in this way. Thus, when applying integration in both members of the equation, it is obtained that:
Unit of measure
Magnetic induction is measured in the International System of Units (SI) in Teslas. This unit of measurement is represented by the letter T, and corresponds to the set of the following basic units.
One tesla is equivalent to the uniform magnetic induction that produces a magnetic flux of 1 weber over a surface of one square meter.
According to the Cegesimal System of Units (CGS), the unit of measurement for magnetic induction is the gauss. The equivalence relationship between both units is as follows:
1 tesla = 10,000 gauss
The unit of measurement for magnetic induction owes its name to the Serbo-Croatian engineer, physicist and inventor Nikola Tesla. It was named this way in the mid-1960s.
How does it work?
It is called induction because there is no physical connection between the primary and secondary elements; consequently, everything happens through indirect and intangible connections.
The phenomenon of electromagnetic induction occurs given the interaction of the lines of force of a variable magnetic field on the free electrons of a nearby conducting element.
For this, the object or medium on which the induction takes place must be arranged perpendicular to the lines of force of the magnetic field. In this way, the force exerted on the free electrons is greater and, consequently, the electromagnetic induction is much stronger.
In turn, the direction of circulation of the induced current is given by the direction given by the lines of force of the variable magnetic field.
On the other hand, there are three methods through which the magnetic field flux can be varied to induce an electromotive force on a nearby body or object:
1- Modify the module of the magnetic field, through variations in the intensity of the flow.
2- Change the angle between the magnetic field and the surface.
3- Modify the size of the inherent surface.
Then, once a magnetic field has been modified, an electromotive force is induced in the neighboring object which, depending on the resistance to current circulation that it possesses (impedance), will produce an induced current.
In that order of ideas, the proportion of said induced current will be greater or less than the primary current, depending on the physical configuration of the system.
Examples
The principle of electromagnetic induction is the basis of operation of electrical voltage transformers.
The transformation ratio of a voltage transformer (step-down or step-up) is given by the number of windings that each transformer winding has.
Thus, depending on the number of coils, the voltage on the secondary may be higher (step-up transformer) or lower (step-down transformer), depending on the application within the interconnected electrical system.
In a similar way, electricity-generating turbines in hydroelectric centers also operate thanks to electromagnetic induction.
In this case, the turbine blades move the axis of rotation that is located between the turbine and the generator. This then results in the mobilization of the rotor.
In turn, the rotor is made up of a series of windings that, when in motion, give rise to a variable magnetic field.
The latter induces an electromotive force in the generator's stator, which is connected to a system that allows the energy generated during the process to be transported online.
Through the two examples set out above it is feasible to detect how electromagnetic induction is part of our lives in elementary applications of everyday life.
References
- Electromagnetic induction (sf). Recovered from: electronics-tutorials.ws
- Electromagnetic induction (sf). Recovered from: nde-ed.org
- Today in history. August 29, 1831: Electromagnetic induction was discovered. Recovered from: mx.tuhistory.com
- Martín, T., and Serrano, A. (nd). Magnetic induction. Polytechnic University of Madrid. Madrid Spain. Recovered from: montes.upm.es
- Sancler, V. (sf). Electromagnetic induction. Recovered from: euston96.com
- Wikipedia, The Free Encyclopedia (2018). Tesla (unit). Recovered from: es.wikipedia.org