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Induction

NAME: Induction

ALTERNATIVE NAME/S: (electro-)Magnetic Induction

DETAILS/DESCRIPTION: Without the principle of induction, we would have no telegraphs, no telephones, no electric lights, electric motors, or digital computers.

Induction links magnetism with electricity. Although these two natural phenomena had been known and studied for centuries, it was not until the early 19th century that Englishman Michael Faraday* discovered how one could be transformed into the other.

William Sturgeon had shown that an electrified wire wrapped around an iron bar turned it into a magnet; Faraday demonstrated that spinning a magnet inside a coil of wire caused it to become electrified. Electromagnetism was born.

Around 1862, James Clerk Maxwell theorized that light was also an electromagnetic phenomenon and  this in turn led directly to Einstein’s famous equation E = mc2, which implied that matter and energy were in some way interchangeable.

Faraday's law and relativity

Faraday's law describes two different phenomena: the motional emf generated by a magnetic force on a moving wire (see Lorentz force), and the transformer emf this is generated by an electric force due to a changing magnetic field (due to the differential form of the Maxwell–Faraday equation). James Clerk Maxwell drew attention to the separate physical phenomena in 1861.[21][22] This is believed to be a unique example in physics of where such a fundamental law is invoked to explain two such different phenomena.[23]

Albert Einstein noticed that the two situations both corresponded to a relative movement between a conductor and a magnet, and the outcome was unaffected by which one was moving. This was one of the principal paths that led him to develop special relativity.[24]

Applications

The principles of electromagnetic induction are applied in many devices and systems, including:

Electrical generator

Rectangular wire loop rotating at angular velocity ω in radially outward pointing magnetic field B of fixed magnitude. The circuit is completed by brushes making sliding contact with top and bottom discs, which have conducting rims. This is a simplified version of the drum generator.

Main article: Electric generator

The emf generated by Faraday's law of induction due to relative movement of a circuit and a magnetic field is the phenomenon underlying electrical generators. When a permanent magnet is moved relative to a conductor, or vice versa, an electromotive force is created. If the wire is connected through an electrical load, current will flow, and thus electrical energy is generated, converting the mechanical energy of motion to electrical energy. For example, the drum generator is based upon the figure to the bottom-right. A different implementation of this idea is the Faraday's disc, shown in simplified form above.

Today superstring theory hopes to take induction to its logical conclusion and achieve the centuries-old dream of showing that all natural forces (electricity, light, gravity, and the strong and weak nuclear forces) are in fact versions of each other.

ONELINER: Induction

OTHER CONNECTIONS: None

BIBLIOGRAPHY:

•        R. Rollefson, H.T. Richards, M.J. Winokur, “EC-7d  Induction - Faraday Discovery”, from their online Physics 202/208 Lab Manual, 2001, http://badger.physics.wisc.edu/lab/manual2/node11.html

Electromagnetic induction - Wikipedia