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Electrotechnology I -- Galvanic Music

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September 19, 2014

In 1819, Hans Christian Andersen discovered that a magnetic compass needle could be deflected by a nearby electrified wire.  Thus began the electromechanical technologies.

In the 1820s, Andre Marie Ampere coined the word  “solenoid” for his coiled wire form that intensified the magnetic field that could be generated.  The following decade saw Joseph Henry laying the groundwork for the telegraph by refining the iron core solenoid, further strengthening the magnetic field and arranging for it to produce an effect useful in long-distance communications.  The effect was audible clicking, not speech.

In 1837, Charles Grafton Page heard “galvanic music” emanating from an iron bar near a coil.  The “music” fleetingly appeared at the moment of contact or disconnection of a battery to the coil.  Around 1841, James Prescott Joule was the first systematic investigator of this contraction of an iron bar in a magnetic field, determining that magnetostriction of iron was too small to be a motor.  (By the way, the word "magnetostriction" is a combination of magnetic and constriction:  iron shrinks in a magnetic field.)

“Pressure electricity” was discovered by the brothers Curie, Pierre and Jacques, in 1880.  An electric charge could be made to appear by compressing a piezoelectric crystal, originally quartz.  The reverse effect of charging a piezoelectric crystal and measuring its displacement was promptly predicted and discovered.

The magnetostrictive and piezoelectric effects mostly languished as physics curiosities for the next few decades.

An introduction of electrotechnologies useful for continuously-controllable fuel injection is incomplete without a small sidebar describing the operating principle of the telephone.  The key to the telephone was its capacity to transmit intelligible speech.  Alexander Graham Bell’s lengthy court battle over his patent conclusively proved that his electromechanical transducers could uniquely transmit and reproduce intelligible speech whereas all attempts to reproduce intelligible speech by adapting solenoid telegraph technology could not be forced to work.

Just like reproducing intelligible speech, the key to continuously-controllable fuel injection is the ability of the injector to vary the fuel flow rate exactly as required.  This is possible only with piezoelectric or magnetostrictive electrotechnology.

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