19th Century Inventions
Towards the end of the 19th century several researchers were developing ways and means of converting sound into electrical signals. The first usable carbon microphone was invented by David Edward Hughes (1831–1900).
Basically, the carbon microphone depends on the variation of contact resistance of granular carbon with applied pressure. An important version of this microphone is the telephone transmitter in which sound-pressure variations are transmitted to the carbon granules through a diaphragm. The corresponding changes of resistance are detected by fluctuations in a current passed through the granules.
Electric power became more and more important as the 20th century approached. Greater powers could be generated when in 1889 the steam turbine became available for driving dynamos. A year earlier, Nikola Tesla (1846–1943), a Croatian engineer who emigrated to the USA in 1884 where he worked for Edison, had developed the alternating current induction motor, eliminating the commutator and sparking brushes required by direct-current motors. The patent for this development was lodged in Britain (British Patent No.6482 dated 1888). Tesla set up a partnership with George Westinghouse to commercialize the induction motor. He is now remembered by the tesla (T), the SI unit of magnetic flux density.
By the end of the 19th century, electrical engineering had effectively split into two branches: one retaining the name electrical engineering; and the other called electronics.
In 1883, Paul Gottlieb Nipkow (1860–1940) discovered television’s scanning principle in which light intensities of an image are sequentially analysed and transmitted. He used for this a rotating disk – the Nipkow disk – with one or more spirals of apertures that passed successively across the image. At the receiving end, a similar disk rotating in synchrony with the scanning disk, and behind which a neon lamp was placed, reproduced the image elements. Although in the past some people considered Nipkow the inventor of television, it is now generally accepted that Vladimir Kosma Zworykin (1889–1982), a Russian-born American engineer is the father of modern television.
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