Техническое чтение для энергетиков. Бухарова Г.П. - 54 стр.

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56
the first, shy attempts to make this force of Nature do some work. Now we are
concerned with the development of electricity for the transmission of energy.
One day in 1819 a Danish physicist, Hans Christian Oersted, was lecturing at
the University of Kiel, which was then a Danish town. Demonstrating a galvanic bat-
tery, he held up a wire leading from it when it suddenly slipped out of his hand and
fell on the table across a marine's compass that happened to be there. As he picked up
the wire again he noticed to his astonishment that the needle of the compass no longer
pointed north, but had swung completely out of position. He switched the current off,
and the needle pointed north again.
For a few months he thought over this incident, and eventually wrote a short
report on it. No one could have been more surprised than Oersted at the extraordinary
impact which his discovery made on physicists all over Europe and America. At last
the longsought connection between electricity and magnetism had been found! Yet
neither Oersted nor his colleagues could forsee the importance of this phenomenon,
for it is the connection between electricity and magnetism on which the entire
practical use of electricity in our time is foundedy
What was it that Oersted had discovered? Nothing more than that an
electrically charged conductor, such as the wire leading from a battery, is the centre
of a magnetic 'field', and this has the effect of turning a magnetic needle at a right
angle with the direction in which the current is flowing; not quite at a right angle,
though, because the magnetism of the earth also influences the needle. Now the
physicists had a reliable means of measuring the strength of a weak electric current
flowing through a conductor; the galvanoscope, or galvanometer, is such a simple
instrument consisting of a few wire loops and a magnetic needle whose deflection
indicates the strength of the current.
Prompted by the research work of Andre-Marie Ampere, the great French
physicist whose name has become a household word as the unit of the electric
current, the Englishman Sturgeon experimented with ordinary, non-magnetized iron.
He found that any piece of soft iron could be turned into a temporary magnet by
putting it in the centre of a coil of insulated wire and making an electric current flow
through the coil. As soon and as long as the current was turned on the iron was
magnetic, but it ceased to be a magnet when there was no more current. Sturgeon
built the first large electro-magnet, and. with this achievement there began the
development of the electrical telegraph and later the telephone.
But there was yet another, and perhaps even more important, development
which began with the electro-magnet. Michael Faraday repeated the experiments of
Oersted, Sturgeon, and Ampere. His brilliant mind conceived this idea: if electricity
could produce magnetism, perhaps magnetism could produce electricity!
But how? For a long time he searched in vain for an answer. Every time he
went for a walk in one of London's parks he carried a little coil and a piece of iron in
his pocket, taking them out now and then
1
to look at them. It was on such a walk that
he found the solution. Suddenly, one day in 1830, in the midst of Green Park (so the
story goes), he knew it: the way to produce electricity by magnetism was – by
motion. He hurried to his laboratory and put his theory to the test. It was correct.

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