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SUPPLEMENT

Text 1
From the History of Electricity

There are two types of electricity, namely, electricity at rest or
in a static condition and electricity in motion, that is, the electric
current. Both of them are made up of electric charges, static
charges being at rest, while electric current flows and does work.
Thus they differ in their ability to serve mankind as well as in their
behaviour.
Let us first turn our attention to static electricity. For a long
time it was the only electrical phenomenon to be observed by man.
At least 2,500 years ago, or so, the Greeks knew how to get
electricity by rubbing substances. However, for practical purposes
static electricity was not much more useful than lightning. Indeed,
the electricity to be obtained by rubbing objects cannot be used to
light lamps, to boil water, to run electric trains, and so on. It is
usually very high in voltage, difficult to control; besides it
discharges in no time.
As early as 1753, Franklin made an important contribution to
the science of electricity. He was the first to prove that unlike
charges are produced due to rubbing dissimilar objects. To show
that the charges are unlike and opposite, he decided to call the
charge on the rubber – negative and that on the glass – positive.
In the connection one might remember the Russian
Academician Petroff. He was the first to carry on experiments and
observations on the electrification of metals by rubbing them one
against another; as a result he was the first scientist in the world
who solved that problem.
So far, almost nothing was said about the electric current.
Who does not know that the first man to produce it was Volta. His
discovery developed out of Galvani’s experiments with the frog.
Various writers retell that story in quite different ways. In fact,
Galvani observed that the legs of a dead frog jumped as a result of
an electric charge. He tried his experiment several times and every
time he obtained the same result. He thought that electricity was
generated within the leg itself. This thought was not so very
strange because he could not help remembering the electric fish
which possessed the property of giving more or less strong shocks.

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