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ELECTRIC-CURRENT-IN-A-GAS
Although a voltaic arc in its natural form as lightning is older than humanity, the
mechanisms behind it were discovered no earlier then the first half of the 19th
century. In a voltaic arc, a part of the electric charge is transported by electrons in a
process that is comparable with that of an electric current in a solid. In contrast to
free electrons in a conductive solid however, electrons involved in a voltaic arc will
often leave their (conduction) band due to fierce collisions between atoms or
between an atom and a previously freed electron. The electric charge of the nucleus
of an atom initially equals the sum of the charges of its surrounding electrons. When
one of these electrons escapes in the process of a collision, the net charge of the
remaining atom will become positive and such a positively charged atom is called an
ion. Since atoms in a gaseous environment are not bound into a grid as they are in
solids, these ions can move more or less freely through space and contribute to the
net displacement of charge albeit in opposite direction and opposite charge as
electrons.
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