Elcectromagnetic Induction

Electromagnetic induction

Electromagnetic induction is the production of a potential differnce across a conductor when it is exposed to a varying magnetic feild.

Speaker

In 1877, German, Ernst Siemens patented the first loudspeaker on Dec. 14, 1877. Englishmen, Sir Oliver Lodge received the second patent for a loudspeaker on April 27, 1898. This was all before music was electrified.In 1924, two General Electric researchers, Chester W. Rice and Edward Washburn Kellogg patented the modern, moving coil, direct radiator, loudspeaker, which become the prominent design for all loudspeakers.
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Microphones

A microphone is an example of a transducer, a device that changes information from one form to another. Sound information exists as patterns of air pressure; the microphone changes this information into patterns of electric current. The recording engineer is interested in the accuracy of this transformation, a concept he thinks of as fidelity.

A variety of mechanical techniques can be used in building microphones. The two most commonly encountered in recording studios are the magneto-dynamic and the variable condenser designs.

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Hans Christian Oersted

One of the most distinguished scientific discoverers and physicists of his time, Oersted was born in 1777 at Rudkjobing. During his residence at Berlin, he wrote his famous essay on the identity of chemical and electrical forces, in which he first developed the ideas on which were based his great discovery of the intimate connection existing between magnetism and electricity. During his residence at Berlin, he wrote his famous essay on the identity of chemical and electrical forces, in which he first developed the ideas on which were based his great discovery of the intimate connection existing between magnetism and electricity and galvanism. This discovery, which formed one of the most important eras in the history of of physical science, obtained for Oersted the Copley Medal from the Royal Society of England, and the principal mathematical prize in the gift of the Institute of Paris. The original and leading idea of this great discovery had been in his mind since 1800. He is one of the greatest scientific benefactors of his times. He died march 9th, 1851.
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