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# What is the Faraday Law?

We explain to you what Faraday’s law is, electromagnetic induction, its history, formula and examples. Also, Lenz’s law.

1. ### What is the Faraday Law?

Faraday’s Electromagnetic Induction Law, known simply as Faraday’s Law, is a principle of physics formulated by British scientist Michel Faraday in 1831. This law quantifies the relationship between a changing magnetic field and the electric field created by its changes.

The statement of said law states:

“The voltage induced in a closed circuit is directly proportional to the speed with which the electromagnetic influx that crosses any surface with the circuit itself as an edge changes over time.”

Which means that in any closed circuit, the electromagnetic force is equivalent to the speed of variation  of the magnetic flux of the circuit.

But to fully understand this, it will be necessary to review Faraday’s experiment: a battery supplied current to a small coil, creating a magnetic field , through turns (metal wires wound on its own axis) that intensify the flow of energy when operating in Serie.

Then, by introducing the small coil into a large one, to force the friction of the magnetic fields, electricity is generated, whose properties can be measured in a galvanometer.

From this experiment and the formulation made by Faraday, numerous conclusions are drawn regarding the generation of electrical energy , which were key to Lenz’s Law and to the modern management of electricity.

Michael Faraday (1791-1867) was a central scientist in the modern western tradition, father of central ideas about electricity and magnetism such as lines of force or the electromagnetic field.

Faraday was greatly excited when Danish physicist Oersted accidentally demonstrated the relationship between electricity and magnetism in 1820 . Therefore, Faraday built a device using a galvanometer connected to an iron ring, which was in turn connected to a battery and a switch, all in closed circuit.

He noticed, then, that when he opened and closed the switch, the galvanometer registered small changes, which he attributed to changes in magnetic flux over time, which led him to formulate his famous law.

Consequently, Faraday was the first to demonstrate the relationship between magnetic fields and electric fields , as can be seen from his experiment reported in the previous section. In fact, the equation of Faraday’s Law became part of Maxwell’s statements.

Faraday’s law is usually expressed by the following formula:

FEM (Ɛ) = dϕ / d t

Where FEM or Ɛ represent the induced Electromotive Force (voltage), and the rest is the rate of temporal variation of the magnetic flux ϕ.

1. ### Examples of Law Enforcement

Virtually all electrical technology is based on Faraday’s law , especially as regards generators, transformers and electric motors.

For example, the DC motor was based on the use of a metal loop rotating in a motionless electric field, whose contacts when moving on conductive metals would generate electricity as it moves on its axis.

That is, by moving a magnetic field you can take advantage of the difference in electrical intensity generated and transform it into work, heat, etc. From this seemingly simple principle follows the invention of such complex things as a transformer, an alternating current generator, a magnetic brake or an electric cooker .

1. ### Lenz’s Law

This law comes from the application of the principle of conservation of energy to the electromagnetic field , in order to obtain the conclusion that the voltages or voltages that are applied to a conductor produce an EMF that opposes any variation of the original current that produced it .

This translates, in mathematical terms, into the addition to Faraday’s law of a negative sign, being formulated in this way:

FEM (Ɛ) = – (dϕ / d t )

This law is essential to determine and control the direction in which the electrical flow of a circuit travels . Its name is because the German scientist Heinrich Lenz formulated it in 1834.