Техническое чтение для энергетиков. Бухарова Г.П. - 20 стр.

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22
the First's physician-in-ordinary, who set the ball rolling.
He experimented with
amber and lodestone and found the essential difference between electric and magnetic
attraction. For substances which behaved like amber – such as glass, sulphur, sealing-
wax – he coined the term 'electrica', and for the phenomenon as such the word
'electricity'. In his famous work De magnete, published in 1600, he gave an account
of his studies. Although some sources credit him with the invention of the first
electric machine, this was a later achievement by Otto von Gue-ricke, inventor of the
air pump.
Von Guericke's electric machine consisted of a large disc spinning between
brushes; this made sparks leap across a gap between two metal balls. It became a
favourite toy in polite society but nothing more than that. In 1700, an Englishman by
the name of Francis Hawksbee produced the first electric light: he exhausted a glass
bulb by means of a vacuum pump and rotated it at high speed while rubbing it with
his hand until it emitted a faint glow of light.
A major advance was the invention of the first electrical condenser, now called
the Leyden jar, by a Dutch scientist, a water-filled glass bottle coated inside and out
with metallic surfaces, separated by the non-conducting glass; a metal rod with a
knob at the top reached down into the water. When charged by an electric machine it
stored enough electricity to give anyone who touched the knob a powerful shock.
More and more scientists took up electric research. A Russian scientist
Professor Richmann from St. Petersburg, was killed when he worked on the same
problem.
Benjamin Franklin, born in Boston, was the fifteenth child of a poor soap-boiler
from England. He was well over 30 when he took up the study of natural phenomena.
'We had for some time been of opinion, that the electrical fire was not created
by friction, but collected, being really an element diffused among, and attracted by
other matter, particularly by water and metals,' wrote Franklin in 1747. Here was at
last a plausible theory of the nature of electricity, namely, that it was some kind of
'fluid'. It dawned on him that thunderstorms were merely a discharge of electricity
between two objects with different electrical potentials, such as the clouds and the
earth. He saw that the discharging spark, the lightning, tended to strike high buildings
and trees, which gave him the idea of trying to attract the electrical 'fluid' deliberately
to the earth in a way that the discharge would do no harm.
In order to work this idea out he undertook his famous kite-and-key
experiment
1
in the summer of 1752. It was much more dangerous than he realized.
During the approach of a thunderstorm he sent up a silken kite with an iron tip; he
rubbed the end of the kite string, which he had soaked in water to make it a good
conductor of electricity, with a large iron key until sparks sprang from the string –
which proved his theory. Had the lightning struck his kite he, and his small son whom
he had taken along, might have lost their lives.
In the next experiment he fixed an iron bar to the outer wall of his house, and
through it charged a Leyden jar with atmospheric electricity. Soon after this he was
appointed Postmaster General of Britain's American colonies, and had to interrupt his
research work. Taking it up again in 1760, he put up the first effective lightning-

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