Dynamos

The mechanical seal was developed ar rhe beginning of the last century. Its development coincided with the invention of the steam turbine, rhe dynamo and the electric motor. 

The electrical age was built on the discovery in the early 1830s, independently by Joseph Henry (1797-1878) in America and Michael Faraday (1791-1867) in England, of electromagnetic induction, which led directly to the invention of the dynamo to generate electricity from steam-powered rotation. It came to fruition on New Year s Eve, 1879, when Thomas Edison (1847-1931) in rural New Jersey, after systematic and exhaustive experiments, made the first successful incandescent lamp, employing a carbonised filament made from some thread taken from Mrs. Edison s sewing cabinet. The lamp burned undimmed for 40 h, watched anxiously by Edison and some of his numerous collaborators. This lamp was ideal for... 

Some of Edison s commercial inventions were produced solely to break the monopolies of patents already granted. Many others represented improvements or changes of known devices these included Edison s electric light and dynamo and his quadraplex tclcgi aph and impro V cd telephone transmitter. This does not detract from the importance of his work, because in the cases of the electric light and dynamo, in particular, his work led to commercially practical devices that were widely adopted. Although some inventions, such his motion picture apparatuses, were not the result of his work alone, hut the result of the joint efforts of the staff of the laboratoiy, Edison s contribution as leader in these projects cannot he ignored. 

The new dynamos made arc lighting economically feasible, especially for street lights. Initial installations were made in Paris in 1877, London at the end of 1878, San Francisco in 1879, and New York in 1880. The other principal commercial application in those early years was for electroplating. 

Large-scale crude oil exploitation began in the late nineteenth century. Internal combustion engines, which make use of the heat and kinetic energy of controlled explosions in a combustion chamber, were developed at approximately the same time. The pioneers in this field were Nikolaus Otto and Gottleib Daimler. These devices were rapidly adapted to military purposes. Small internal-combustion motors were used to drive dynamos to provide electric power to fortifications in Europe and the United States before the outbreak of World War I. Several armies experimented vith automobile transportation before 1914. The growing demand for fossil fuels in the early decades of the twentieth centuiy was exacerbated by the modernizing armies that slowly introduced mechanization into their orders of battle. The traditional companions of the soldier, the horse and mule, were slowly replaced by the armored car and the truck in the early twentieth century. 

Sperry applied for his first patent—a dynamo-electric machine— when he was twenty. His final patent application—for a variable pitch propeller— was submitted in 1930, shortly after his death. In total, 355 of his over 400 patent applications matured as actual granted patents. 

Figure 2-69 is a schematic of perhaps the simplest rotating machine, the elementary dynamo. The elementary dynamo consists of a rectangular-shaped coil, which is free to rotate about an axis. In a practical device, the coil is physically attached to a shaft... 

Note that the direction of the applied torque will dictate the direction of the induced current in the elementary dynamo. 

Thus from Equation 2-215 we see that for a given dynamo geometry, the developed torque only depends on the interaction between two magnetic fields and their orientation with respect to each other. One or both of the magnetic fields may be induced by a current. If one of the fields is the field of a magnet, then it may be either in the rotor or the stator. If the rotation results from the imposition of mechanical power on the rotor, the device is called a generator. If the rotation is caused by the flow of current, the device is called a motor, i.e., converts electric power to mechanical power. 

If the rotor of the elementary dynamo is turned in a uniform magnetic field, an AC emf and current are produced. If the speed of rotation is constant, the emf and current are sinusoidal as shown in Figure 2-69. 

If the slip rings of the elementary dynamo are replaced by a split-ring commutator, then a DC emf and current will be generated as shown in Figure 2-71. If the single... 

Steam, gas, petrol, and hot-air engines are heat engines a thermopile coupled with an electromotor also constitutes a heat engine. An electromotor is not a heat engine, since its effect is produced at the cost of electrical energy, which may, it is true, ultimately be derived from a heat engine coupled with a dynamo, but may equally well arise from chemical action in voltaic cells absorbing practically no heat from their environment (e.g., the Daniell cell). 

This definition excludes such sources of current as thermocouples, or dynamos, in which all the materials composing the element remain unchanged. 

Chemistry Industry No. 10, 16th May 1994, p.366 FROM DUSTBIN TO DYNAMO Nathan S... 

Engines. Vehicular petrol engines are potential ignition sources by means of the spark-ignition system, dynamo or battery, or hot exhaust pipe. Non-flameproof diesel engines are potential ignition sources due to a hot exhaust pipe or carbonaceous particles or flames from the exhaust. 

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