Conductors and insulators

All atoms are electrically neutral i.e. they have the same amounts of negative and positive
charge inside them. By convention, the electrons carry negative charge and the protons carry
positive charge.
The basic unit of charge, called the elementary charge, e, is
the amount of charge carried by one electron.All the matter and materials on earth are made up of atoms.
Some materials allow electrons to move relatively freely
through them (e.g. most metals, the human body).
These materials are called conductors.Other materials do not allow the charge carriers, the electrons, to move
through them (e.g. plastic, glass).
The electrons are bound to the atoms in the material. These materials are called
non-conductors or insulators.If an excess of charge is placed on an insulator, it will stay
where it is put and there will be a concentration of charge in
that area of the object. However, if an excess of charge is placed
on a conductor, the like charges will repel each other
and spread out over the outside surface of the object. When two conductors
are made to touch, the total charge on them is shared between the
two. If the two conductors are identical, then each conductor will
be left with half of the total charge.