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Conduction in Gases
Gases normally contain few free electrons and are generally insulators.
When a strong potential difference is applied between two points inside a
container filled with a gas, the few free electrons are accelerated by the
potential difference and collide with the atoms of the gas, knocking free more
electrons. The gas atoms become positively charged ions and the gas is said to
be ionized.
(F)
_______________________ An electric current in a gas is
composed of these opposite flows of charges.
Conduction in Liquid Solutions
Many substances become ionized when they dissolve in water or in some
other liquid. An example is ordinary table salt, sodium chloride (NaCl). When
sodium chloride dissolves in water, it separates into positive sodium ions, Na+,
and negative chlorine ions, Cl-. If two points in the solution are at different
potentials, the negative ions drift toward the positive point, while the positive
ions drift toward the negative point.
(G)
________________ Thus, while water
that is absolutely pure is an insulator, water that contains even a slight impurity
of an ionized substance is a conductor.
Since the positive and negative ions of a dissolved substance migrate to
different points when an electric current flows, the substance is gradually
separated into two parts.
(H)
____________________
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