Re: Why does carbon conduct electricity?

Materials such as metals, conduct electricity do so because when their
atoms are arranged together in a solid, they have loosely bound electrons
which can easily move through the material if an electric potential is
applied to it.

For instance, in a copper lattice, there is about one free electron
available per atom of copper for conduction, which makes it a very good
conductor of electricity.

But,carbon holds on more tightly to its electrons so they are not as free
to move from place to place as in the case of copper or other metals.
It is one of a number of elements known as semiconductors. Its neighbor,
one row down on the periodic table, is silicon, which is used for most
commercial microchips produced today.

In a semiconductor, electrons can't just flow through the material. They
have to move from atom to atom in "jumps", according to the laws of
quantum mechanics. When they jump, they leave a positively charged "hole",
which can be later filled by another electron jumping in to take the
first electron's place. Under the influence of an electric potential, one
sees a slow movement of negatively charged electrons in one direction and
positively charged "holes" in the other direction. 

If you warm up a semiconductor, the outer electrons are more energetic,
and can more easily jump from atom to atom. So, the performance of many
microchips and other semiconductor devices varies with temperature, and
a carbon resistor can be used as a crude thermometer by measuring how
well it conducts electricity at different temperatures.

I hope this helps.