Magnetic induction


Today, it is difficult to imagine a world without generators and without electric motors. This is a contribution that we owe to the researcher Michael Faraday, who discovered magnetic induction , as well as to contemporary scientists of his time. Magnetic induction refers to the process in which a time-varying magnetic field produces an electric field . This phenomenon has various applications in the technological field. Indeed, almost all electricity production is based on the magnetic induction process. For example, electric batteries, generators, transformers, electric motors, among other devices, work based on the principles of magnetic induction.What is magnetic induction?


Magnetic induction is the phenomenon through which a magnetic field generates an electric field . When an electric field is generated in a conductive material, the charge carriers are exposed to a force and an electric current is induced in the conductor.

  • What is magnetic induction
  • Who discovered
  • History
  • How Magnetic Induction Is Calculated
  • Magnetic induction lines
  • Examples

What is magnetic induction

This phenomenon consists of the generation of an electromotive force in a medium or body subjected to a variable magnetic field . It can also happen that this force is generated in a moving medium exposed to a static magnetic field. This being the case, when it is a conducting body, an induced electric current is originated.


Magnetic induction is then a phenomenon that depends intrinsically on time , in the strict sense, and that comes out of the field of magneto-static (studies of stationary magnetic phenomena).

Who discovered

In 1831, Michael Faraday (1791-1867) discovered in England, the phenomenon of magnetic induction when he realized that a variable magnetic field produces an electric field . On the other hand, James Clerk Maxwell was the one who described the process mathematically and called it Faraday’s law of induction.


On August 29, 1831 , the Englishman Michael Faraday, discovered magnetic induction, the interaction of electricity and magnetism that allows the creation of the electric induction motor and generator, among other things. The application of this knowledge was present in the electrical period of man, since the use of modern devices was possible with the use of the magnetic induction process.

The crucial experiment that allows Michael Faraday to establish his law is very simple. In fact, it can be easily reproduced with objects from everyday life. Faraday wrapped an insulated iron wire around a cardboard tube to form a coil. Next, he connected a voltmeter to the ends of the coil and measured the electromotive force induced when a magnet in the coil was displaced.

How Magnetic Induction Is Calculated

The magnetic induction process is represented by the letter B . Its calculation is carried out as follows:

Magnetic induction formula

Where: B the magnetic induction, Φ the magnetic flux and S the surface

Magnetic induction lines

Magnetic induction lines are one way to represent a magnetic field . For Faraday, the lines of force are chains of polarized particles in a dielectric and these can have an existence of their own throughout a wide space. For their part, JJ Thomson and Maxwell refer to induction lines as electrostatic induction tubes or simply as Faraday tubes .

In the 20th century, lines of force are energy connections incorporated into the unified theoretical perspective of the 19th century, which is more mathematical and sophisticated.


Example 1

A coil travels down the axis of a cylindrical magnet magnetized along its axis. In this case, an ammeter will measure the induced current in the coil.

Since there is no electric field since the magnet is neutral, the force is qv x B. In view of the axial symmetry in this case, the electromotive force adds along the wire and a current flows in the coil.

Example 2

A copper disk rotates around a magnet and the circuit is completed by an immobile wire that travels on the outside of the disk . The electrons in the copper disk are carried through the field lines resulting in an electromotive force. The rest of the circuit remains immobile and does not favor the electromotive force. Since the field lines cut the conductor once, a net electromotive force is obtained. Although there is no flux change in the loop, an electromotive force is induced.

Example 3

If a magnet is placed with the north pole pointing downward , the current in the coil will flow in the counterclockwise direction if the right hand grip rule is applied.

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