The following sections of this BookRags Literature Study Guide is offprint from Gale's For Students Series: Presenting Analysis, Context, and Criticism on Commonly Studied Works: Introduction, Author Biography, Plot Summary, Characters, Themes, Style, Historical Context, Critical Overview, Criticism and Critical Essays, Media Adaptations, Topics for Further Study, Compare & Contrast, What Do I Read Next?, For Further Study, and Sources.
(c)1998-2002; (c)2002 by Gale. Gale is an imprint of The Gale Group, Inc., a division of Thomson Learning, Inc. Gale and Design and Thomson Learning are trademarks used herein under license.
The following sections, if they exist, are offprint from Beacham's Encyclopedia of Popular Fiction: "Social Concerns", "Thematic Overview", "Techniques", "Literary Precedents", "Key Questions", "Related Titles", "Adaptations", "Related Web Sites". (c)1994-2005, by Walton Beacham.
The following sections, if they exist, are offprint from Beacham's Guide to Literature for Young Adults: "About the Author", "Overview", "Setting", "Literary Qualities", "Social Sensitivity", "Topics for Discussion", "Ideas for Reports and Papers". (c)1994-2005, by Walton Beacham.
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In 1769, the first self-powered carriage was produced by Nicholas-Joseph Cugnot, a French military engineer. The machine's power was steam-generated and required so much cumbersome equipment that it was unmanageable and inefficient. It quickly became obvious that a more effective machine had to be developed. John Barber was the first to act on the theory of using a combination of highly condensed air and fuel to drive these self-powered carriages. He used matches and candles to produce the spark necessary to ignite the fuel and create the drive force. He patented his gas turbine in 1791.
It was not until 1860, however, that Frenchman, Jean-Joseph-Étienne Lenoir developed the earliest version of the internal combustion engine that used an electrical spark from a spark plug to ignite an air-fuel mixture. Lenoir's spark plug consisted of a hollow brass bolt, porcelain, and two platinum wires. Later, in 1885, Lenoir refined his spark plug, and the later version closely resembles what is used today.
Timing of combustion is controlled by the ignition system, but the spark plug's task is to produce the spark. Voltage from the ignition system ionizes (removes electrons from) air molecules around the electrodes of the spark plug. The voltage concentrates along a sharp edge of the electrode, causing a spark to arc across the electrode and ignite the exposed fuel. Sparking wears away the edges of the electrodes, so spark plugs have to be replaced periodically.
Modifications to spark plug design have been part of the search for internal combustion engines that burn leaner air-fuel mixtures and run cleaner. Metal alloys improve thermal conductivity; gold-palladium, copper-core and platinum-tipped plugs are claimed by spark plug makers to be more durable and to fire more reliably. The shape and exposure of the electrode improves combustion efficiency, and the two-pronged side electrode has been proven to improve fuel economy and engine performance. Specialized plugs like the Halo Disc are made of tungsten, nickel, and iron and have specialized insulators, electrodes, and inductors to minimize fouling, quenching, and electromagnetic interference. Such design features account for the wide assortment of spark plugs on the market.