electromagnetic induction

Also found in: Dictionary, Thesaurus, Medical, Legal, Financial, Acronyms, Wikipedia.
Related to electromagnetic induction: magnetic flux

induction

, in electricity and magnetism
induction, in electricity and magnetism, common name for three distinct phenomena. Electromagnetic induction is the production of an electromotive force (emf) in a conductor as a result of a changing magnetic field about the conductor and is the most important of the three phenomena. It was discovered in 1831 by Michael Faraday and independently by Joseph Henry. Variation in the field around a conductor may be produced by relative motion between the conductor and the source of the magnetic field, as in an electric generator, or by varying the strength of the entire field, so that the field around the conductor is also changing. Since a magnetic field is produced around a current-carrying conductor, such a field can be changed by changing the current. Thus, if the conductor in which an emf is to be induced is part of an electric circuit, the induction can be caused by changing the current in that circuit; this is called self-induction. The induced emf is always such that it opposes the change that gives rise to it, according to Lenz's law. Changing the current in a given circuit can also induce an emf in another, nearby circuit unconnected with the original circuit; this type of electromagnetic induction, called mutual induction, is the basis of the transformer. Electrostatic induction is the production of an unbalanced electric charge on an uncharged metallic body as a result of a charged body being brought near it without touching it. If the charged body is positively charged, electrons in the uncharged body will be attracted toward it; if the opposite end of the body is then grounded, electrons will flow onto it to replace those drawn to the other end, the body thus acquiring a negative charge after the ground connection is broken. A similar procedure can be used to produce a positive charge on the uncharged body when a negatively charged body is brought near it. See electricity. Magnetic induction is the production of a magnetic field in a piece of unmagnetized iron or other ferromagnetic substance when a magnet is brought near it. The magnet causes the individual particles of the iron, which act like tiny magnets, to line up so that the sample as a whole becomes magnetized. Most of this induced magnetism is lost when the magnet causing it is taken away. See magnetism.

Electromagnetic induction

The production of an electromotive force either by motion of a conductor through a magnetic field in such a manner as to cut across the magnetic flux or by a change in the magnetic flux that threads a conductor. See Electromotive force (emf)

If the flux threading a coil is produced by a current in the coil, any change in that current will cause a change in flux, and thus there will be an induced emf while the current is changing. This process is called self-induction. The emf of self-induction is proportional to the rate of change of current.

The process by which an emf is induced in one circuit by a change of current in a neighboring circuit is called mutual induction. Flux produced by a current in a circuit A threads or links circuit B. When there is a change of current in circuit A, there is a change in the flux linking coil B, and an emf is induced in circuit B while the change is taking place. Transformers operate on the principle of mutual induction.

The phenomenon of electromagnetic induction has a great many important applications in modern technology.

McGraw-Hill Concise Encyclopedia of Physics. © 2002 by The McGraw-Hill Companies, Inc.
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Electromagnetic Induction

the production of an electromotive force (induced emf) in a conducting circuit located in a variable magnetic field or moving in a constant magnetic field. The electric current induced by this emf is called an induced current. Electromagnetic induction was discovered by M. Faraday in 1831. According to Faraday’s law, the induced emf Ej in a circuit is directly proportional to the rate of change of the magnetic flux (the flux of the magnetic induction vector) ϕ through the surface S bounded by this circuit:

Here ΔΦ is the change in the magnetic flux through the circuit over time Ac the proportionality coefficient k in the International System of Units is equal to k = 1 and in the cgs (Gauss) system, k = 1/c, where c is the velocity of light in a vacuum. The minus sign defines the direction of the induced current in accordance with Lenz’ rule: the direction of the induced current is such that the magnetic induction flux that it creates through the area bounded by the circuit tends to oppose the flux Φ variation that is responsible for the induced current.

In a constant magnetic field an induced emf arises only during the motion of the circuit in which the magnetic flux through the surface bounded by the circuit changes with time (that is, the circuit in its motion must intersect the lines of magnetic flux; when the motion is along the lines, the flux Φ will not change and no emf will arise). In this case the induced emf is equal to the work of the magnetic part of the Lorentz force needed to displace a unit charge along the closed circuit. If, however, a fixed conductor is in a constant magnetic field, the induced emf is equal to the work needed to displace a unit charge along the closed circuit; this work is performed by the forces of a circuital electric field, which, according to Maxwell’s equations, originates in space when a magnetic field changes with time. In a reference system, with respect to which the circuit is at rest, it is precisely this circuital electric field that induces the motion of charged particles, that is, the appearance of an induced current. Electromagnetic induction underlies the operation of electric current generators, in which mechanical energy is transformed into electrical; the operation of transformers and other equipment is also based on this phenomenon.

REFERENCE

Kalashnikov, S. G. Elektrichestvo. Moscow, 1970. Chapter 9. (Obshchiikurs fiziki, vol. 2.)

G. IA. MIAKISHEV

electromagnetic induction

[i¦lek·trō·mag′ned·ik in′dək·shən]
(electromagnetism)
The production of an electromotive force either by motion of a conductor through a magnetic field so as to cut across the magnetic flux or by a change in the magnetic flux that threads a conductor. Also known as induction.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.

Electromagnetic induction

The production of an electromotive force either by motion of a conductor through a magnetic field in such a manner as to cut across the magnetic flux or by a change in the magnetic flux that threads a conductor. See Electromotive force (emf)

If the flux threading a coil is produced by a current in the coil, any change in that current will cause a change in flux, and thus there will be an induced emf while the current is changing. This process is called self-induction. The emf of self-induction is proportional to the rate of change of current.

The process by which an emf is induced in one circuit by a change of current in a neighboring circuit is called mutual induction. Flux produced by a current in a circuit A threads or links circuit B. When there is a change of current in circuit A, there is a change in the flux linking coil B, and an emf is induced in circuit B while the change is taking place. Transformers operate on the principle of mutual induction. See Transformer

The phenomenon of electromagnetic induction has a great many important applications in modern technology. See Generator, Induction heating, Motor, Servomechanism

McGraw-Hill Concise Encyclopedia of Engineering. © 2002 by The McGraw-Hill Companies, Inc.

electromagnetic induction

A magnetic field that is generated around a conductor when a current flows through it. Electromagnetic induction is also the creation of an electrical pulse in a conductor when a magnetic field moves or collapses around it.

Electromagnetic induction is the principle behind the read/write head on magnetic disks and tapes. To create (write) the bit, current is sent through a coil that creates a magnetic field which is discharged at the gap of the read/write head onto the disk platter as it spins by. To read the bit, the magnetic field of the bit "induces" an electrical charge in the head as it passes by the gap. See inductor and wireless charging.
Copyright © 1981-2019 by The Computer Language Company Inc. All Rights reserved. THIS DEFINITION IS FOR PERSONAL USE ONLY. All other reproduction is strictly prohibited without permission from the publisher.
References in periodicals archive ?
Triantafilis J, Laslett GM, McBratney AB (2000) Calibrating an electromagnetic induction instrument to measure salinity in soil under irrigated cotton.
Huth NI, Poulton PL (2007) An electromagnetic induction method for monitoring variation in soil moisture in agroforestry systems.
The most promising technologies currently are magnetometry and electromagnetic induction, he said.
The purpose of this investigation was to evaluate the use of electromagnetic induction and towed army resistivity methods to assess clay content and identify areas of sand blows in alluvial soils of southeastern Missouri.
Both malleable and compressible, easy to cut and drip-free, it is heated by electromagnetic induction to bring its polymerization time to 90 minutes.
Thermal metamorphism was probably due to a combination of the following heat sources; the decay of short-lived radionuclides, electromagnetic induction during an early T-Tauri stage of the sun, or possibly the brecciated in situ target material being in proximity to an impact-generated melt sheet.
Faraday's discovery of electromagnetic induction that led the way for the wide spread production and use of electricity is by far the most significant scientific achievement.