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Subject: Conductors, insulators, and electron flow : BASIC CONCEPTS OF ELECTRICITY
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and=20
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<H1>Conductors, insulators, and electron flow</H1>
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</DIV><A name=3D"Free electron"></A><A name=3D"Electron, free"></A>
<P>The electrons of different types of atoms have different degrees of =
freedom=20
to move around. With some types of materials, such as metals, the =
outermost=20
electrons in the atoms are so loosely bound that they chaotically move =
in the=20
space between the atoms of that material by nothing more than the =
influence of=20
room-temperature heat energy. Because these virtually unbound electrons =
are free=20
to leave their respective atoms and float around in the space between =
adjacent=20
atoms, they are often called <I>free electrons</I>. </P>
<P>In other types of materials such as glass, the atoms' electrons have =
very=20
little freedom to move around. While external forces such as physical =
rubbing=20
can force some of these electrons to leave their respective atoms and =
transfer=20
to the atoms of another material, they do not move between atoms within =
that=20
material very easily. </P><A name=3DConductivity></A><A =
name=3DConductor></A><A=20
name=3DInsulator></A>
<P>This relative mobility of electrons within a material is known as =
electric=20
<I>conductivity</I>. Conductivity is determined by the types of atoms in =
a=20
material (the number of protons in each atom's nucleus, determining its =
chemical=20
identity) and how the atoms are linked together with one another. =
Materials with=20
high electron mobility (many free electrons) are called =
<I>conductors</I>, while=20
materials with low electron mobility (few or no free electrons) are =
called=20
<I>insulators</I>. </P>
<P>Here are a few common examples of conductors and insulators: =
</P><BR><BR>
<UL>
<LI><B>Conductors:</B>=20
<LI>silver=20
<LI>copper=20
<LI>gold=20
<LI>aluminum=20
<LI>iron=20
<LI>steel=20
<LI>brass=20
<LI>bronze=20
<LI>mercury=20
<LI>graphite=20
<LI>dirty water=20
<LI>concrete </LI></UL><BR><BR>
<UL>
<LI><B>Insulators:</B>=20
<LI>glass=20
<LI>rubber=20
<LI>oil=20
<LI>asphalt=20
<LI>fiberglass=20
<LI>porcelain=20
<LI>ceramic=20
<LI>quartz=20
<LI>(dry) cotton=20
<LI>(dry) paper=20
<LI>(dry) wood=20
<LI>plastic=20
<LI>air=20
<LI>diamond=20
<LI>pure water </LI></UL><BR><BR>
<P>It must be understood that not all conductive materials have the same =
level=20
of conductivity, and not all insulators are equally resistant to =
electron=20
motion. Electrical conductivity is analogous to the transparency of =
certain=20
materials to light: materials that easily "conduct" light are called=20
"transparent," while those that don't are called "opaque." However, not =
all=20
transparent materials are equally conductive to light. Window glass is =
better=20
than most plastics, and certainly better than "clear" fiberglass. So it =
is with=20
electrical conductors, some being better than others. </P>
<P>For instance, silver is the best conductor in the "conductors" list, =
offering=20
easier passage for electrons than any other material cited. Dirty water =
and=20
concrete are also listed as conductors, but these materials are =
substantially=20
less conductive than any metal. </P>
<P>Physical dimension also impacts conductivity. For instance, if we =
take two=20
strips of the same conductive material -- one thin and the other thick =
-- the=20
thick strip will prove to be a better conductor than the thin for the =
same=20
length. If we take another pair of strips -- this time both with the =
same=20
thickness but one shorter than the other -- the shorter one will offer =
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