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to be a material that allows no current flow through it. Common insulator
materials used in electrical devices are paper, wood, plastics, rubber, glass etc.
Notice that common insulators are not pure elements. They are materials in
which two or more elements are joined together to form a new substance. In the
process of joining together, elements share their valence electrons. This sharing
of valence electrons is called covalent bonding. It takes a lot of added energy to
break an electron free of a covalent bond.
Between the extremes of conductors and insulators is a group of materials
known as semiconductors. The basic property of a semiconductor is given by its
name - it “conducts a little bit”. A semiconductor will carry electric current, but
not easily as a normal conductor. Semiconductors are midway between
conductors and insulators. They are
neither
good conductors
nor
good
insulators.
Under certain conditions
they allow a current to flow easily but
under others they behave as insulators. Germanium and silicon are
semiconductors. The total conductivity in semi conducting materials is the sum
of electron current and hole current. Semiconductors are extremely important
industrial materials, they are materials from which electronic devices such as
transistors(an active semiconductor device that has three or more electrodes, i.e.
emitter, base and collector; it can perform practically all the functions of tubes,
including amplification and rectification), diodes, integrated circuits
(
a single
semiconductor chip or wafer which contains thousands or millions of circuit
elements per square centimeter), and solar cells are manufactured.
Without them modern electronic technology would not be possible, it
would be even inconceivable.
Suggest Russian equivalents to the
italicized
parts of the sentences.
What is the function of these words in the sentences? Make your sentences
using them
Say whether these sentences are true or false
1.
Electrical conductivity of a body depends upon its atomic
constitution.
2.
There is no difference in the conducting ability of various substances.
3.
The longer the wire is the weaker its opposition is.
4.
The kind of the insulating material depends upon the purpose it is
meant for.
5.
Conductors are substances through which electricity is easily
transmitted.
6.
Insulators do not allow the electric current to flow freely.
