faraday's law



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

Faraday's law studies the electromagnetic force in a closed circuit.

What is Faraday's Law?

Faraday's Law of Electromagnetic Induction, known simply as Faraday's Law, was formulated by the British scientist Michael Faraday in 1831. This law quantifies the relationship between a changing magnetic field in the weather and the electric field created by these changes.

The statement of said law states:

"The induced voltage in a closed circuit is directly proportional to the rate of change in time of the magnetic flux that passes through any surface with the circuit itself as an edge."

To fully understand this, it will be necessary to review Faraday's experiment: a battery supplied current to a small coil, creating amagnetic field through the turns of the coil (metallic cables wound on their own axis). When this coil was moved in and out of a larger one, its magnetic field (changing over time by the movement) generated a voltage on the large coil that could be measured with a galvanometer.

From this experiment and the formulation of Faraday's law, numerous conclusions regarding the generation of electric power, which were key to Lenz's Law and to the modern management of electricity.

Faraday's law history

Michael Faraday studied electromagnetism and electrochemistry.

Michael Faraday (1791-1867) was the creator of central ideas around the electricity and themagnetism.

Faraday was extremely excited when the Danish physicist Oersted empirically demonstrated the relationship between electricity and magnetism in 1820, noting that a current conducting wire could move a magnetic needle on a compass.

Faraday designed multiple experiments. For example, he wrapped two wire solenoids around an iron ring and saw that when, by means of a switch, he passed current through one of the solenoids, a current was induced in the other. Faraday attributed the appearance of current to changes in the magnetic flux over time.

Consequently, Faraday was the first to demonstrate the relationship between magnetic fields and electric fields, as can be seen from the two experiments described. In fact, the Faraday's Law equation became part of Maxwell's law statements.

Faraday's law formula

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

EMF (Ɛ) = dϕ / dt

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

Faraday's Law Application Examples

Everyday objects like electric ovens are made possible by Faraday's law.

Virtually all electrical technology is based on Faraday's law, especially with regard to generators, transformers and electric motors.

For example, the direct current motor was based on the use of a disk of copper that rotated between the ends of a magnet, generating a DC.

From this seemingly simple principle follows the invention of such complex things as a transformer, a generator of alternating current, a magnetic brake or an electric stove.

Lenz's law

This law comes from the application of theprinciple of conservation of energy to electromagnetic induction, which allows obtaining the conclusion that the EMF produced by a changing magnetic flux (Faraday's law), generates a current with a direction that opposes the variation of the flux that produces it.

This is translated, in mathematical terms, in the addition to Faraday's law of a negative sign, being formulated in this way:

EMF (Ɛ) = - (dϕ / dt)

This law is fundamental to determine and control the direction in which the electrical flow of a circuit travels. Its name comes from the fact that the German scientist Heinrich Lenz formulated it in 1834.

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