We explain what Faraday's law is, electromagnetic induction, its history, formula and examples. Also, Lenz's law.
What is Faraday's Law?
Faraday's Law of Electromagnetic Induction, known simply as Faraday's Law, was formulated by British scientist Michael Faraday in 1831. This law quantifies the relationship between a magnetic field changing over time and the electric field created by these changes.
The statement of said law states:
“The voltage induced in a closed circuit is directly proportional to the rate of change over 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 a magnetic field through the coil's turns (metal cables wound on their own axis). When this coil moved in and out of a larger coil, its magnetic field (changing over time due to movement) generated a voltage across the large coil that could be measured with a galvanometer.
From this experiment and the formulation of Faraday's law, numerous conclusions emerge regarding the generation of electrical energy, which were key to Lenz's Law and to the modern management of electricity.
History of Faraday's law
Michael Faraday (1791-1867) was the creator of central ideas around electricity and magnetism.
Faraday was greatly excited when the Danish physicist Oersted empirically demonstrated the relationship between electricity and magnetism in 1820, verifying that a current-conducting wire could move a magnetic needle of a compass.
Faraday designed multiple experiments. For example, he wound two wire solenoids around an iron ring and found 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 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 equation of Faraday's Law became part of the statements of Maxwell's laws.
Faraday's law formula
Faraday's law is usually expressed by the following formula:
EMF (Ɛ) = dϕ/dt
Where FEM either Ɛ represent the induced electromotive force (tension), and dϕ/dt is the rate of temporal variation of the magnetic flux ϕ .
Examples of application of Faraday's law
Virtually all electrical technology is based on Faraday's law especially what refers to generators, transformers and electric motors.
For example, the dc motor It was based on the use of a copper disc that rotated between the ends of a magnet, generating a direct current.
From this apparently simple principle arises the invention of things as complex as a transformer, an alternating current generator, a magnetic brake or an electric stove.
Lenz's law
This law comes from the application of the principle of conservation of energy to electromagnetic induction, which allows us to conclude that the EMF produced by a changing magnetic flux (Faraday's law) generates a current with a direction that opposes the variation of the flow that produces it
This translates, in mathematical terms, into the addition of a negative sign to Faraday's law, being formulated in this way:
EMF (Ɛ) = -(dϕ/dt)
This law It is essential to determine and control the direction in which the electrical flow of a circuit moves. Its name is due to the German scientist Heinrich Lenz formulating it in 1834.
Continue with: Electrostatics
References
- “Faraday's Law” on Wikipedia.
- “What is Faraday's Law?” at Khan Academy.
- “Faraday's Law” in EspacioCiencia.com.
- “Lenz's Law” in Wikipedia.
- “Electromagnetic induction. Laws of Faraday and Lenz” (video) at Universidad Rey Juan Carlos.
- “Faraday's Law” in Hyperphysics.
- “What is Faraday's Law of Induction?” on LiveScience.
- “Faraday's Law of Induction” in The Encyclopaedia Britannica.
