Basic HTML Version
1
Conductors, insulators,
semiconductors
W
hen electrons can move easily from atom
to atom in a material, that material
is a good conductor. Most metals are good
conductors;
silver
is the best and
copper
is second best. This is because their
atomic structure allows the outermost
1
orbital electrons
to move freely.
Although second best copper wire is
generally used for most conductors because
it costs much less than silver. Conductors
are used so as to allow electric current
to flow as freely as possible.
A material with atoms in which the electrons
tend to stay in their own orbits, tightly
bound to the atom, is an insulator, because
it does not conduct electricity very
easily: wood, glass, plastic, ceramic,
air, cotton. These are all examples of
materials in which electrons stick with
their atoms. Because the electrons don’t
move, these materials can’t conduct
electricity very well, if at all. These
materials are electrical insulators.
However, insulators are able to hold or
store
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electricity better than conductors. An
insulating material, such as glass, plastic,
rubber, paper, air, or mica, is called a
dielectric. A dielectric is able to store an
electric charge. Insulators are very useful
when current flow must be inhibited.
Finally, there are semiconductors —
materials which conduct less well than metal
conductors but better than insulators.
Examples are:
carbon
,
germanium
and
silicon
,
which are commonly used for transistors
and other semiconductor components.
1
outermost
: farthest from the centre
2
store
: put something you are not using in a safe place
Good and Bad Conductors
4
Brainstorming
Before reading the passage, try to guess the meaning of each of the words in the
title and decide what you think each does and is used for. Then read on.
TEXT 2
carbon
carbonio
copper
rame
germanium
germanio
orbital electrons
elettroni orbitanti
silicon
silicio
silver
argento
TECHNICAL ENGLISH
5
Underline the words or sentences which explain the meaning of the words in the title.
Conductors:
.........................................................................................................................................................................................................
Insulators:
..............................................................................................................................................................................................................
Semiconductors:
..............................................................................................................................................................................................
Did you guess right?
YES
NO
Almost!
6
Put these materials into the correct column in the table below.
7
Using the information gathered above, answer the following questions.
a
Why is an insulator called dielectric?
b
Why is copper used more often than silver?
c
When is a semiconductor used?
Conductors
Insulators
Semiconductors
air carbon copper germanium glass mica paper
plastic rubber silicon silver wire
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Progetto FOR ELECTRONICS_unit_1.indd 19
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