Техническое чтение для энергетиков. Бухарова Г.П. - 42 стр.

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44
regard to a hypothesis which he himself had advanced. He became so prejudiced in
favour of his animal magnetism theory that it was quite impossible for him to view
objectively later evidence which definitely contradicted it and finally caused it to be
discarded.
Another Italian, Alessandro Volta (1745–1827), a professor of physics in the
University of Pavia, established the true source of the electric current. He
demonstrated that it could be produced by the action of dissimilar metals without the
presence of animal tissue of any sort.
In the course of his experiments in 1800 he developed the first electric battery,
a device known as a voltaic pile. Although he tried a number of different materials he
found that the best results were obtained when he used silver and zink as the two
metals. The pile consisted of a Befits Of small discs of these and of cardboard, the
latter having been soaked in a salt solution-Then he piled the discs up one on another
in the order silver, zink, cardboard, and so forth, ending with zinc. By connecting
wires to the top and bottom discs he was able to get continuous electric currents
which were of substantial size.
All the essentials of a modern electric cell or battery were present in the voltaic
pile. Developments since that time have been largely directed toward making cells
more convenient to use and toward eliminating various undesirable chemical
reactions.
THE DEVELOPMENT OF ELECTRIC MOTOR
The engine which could convert electric energy into mechanical power was
already in existence. As early as 1822 Faraday outlined the way in which an electric
motor could work: by placing a coil, or armature, between the poles of an electromag-
net; when a current is made to How through the coil the electromagnetic force causes
(I) it to rotate the reverse principle, in fact, of the generator.
The Russian physicist, Jacobi built several electric motors during the middle
decades of the XIXth century. Jacobi even succeeded in running a small, battery-
powered electric boat on the Neva river in St. Petersburg. All of them, however, came
to the conclusion that the electric motor was a rather uneconomical machine so long
as galvanic batteries were the only source of electricity. It did not occur to them that
motors and generators could be made interchangeable.
In 1888, Professor Galileo FerYaris in Turm and Nikola Tesla – the pioneer of
high-frequency engineering'–in America invented, independently and without
knowing of each other's work, the induction motor. This machine, a most important
but little recognized technical achievement, provides no less than two-thirds of all the
motive power for the factories of the world, and much of modern industry could not
do without (2) it. Known under the name of "squirrel-cage motor" – because (3) it
resembles the wire cage in which squirrels used to be kept – (4) it has two circular
rings made of copper or aluminium joined by a few dozen parallel bars of the same
material, thus forming a cylindrical cage.
Although the induction motor has been improved a great deal and its power

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