Insulators
No electrons move through insulators because there are no free electrons that can move through the solid lattice.
The electrons are attached to the atoms. These electrons are in the valence energy band.
Metallic Conductors
Most of the electrons are attached to the atom and are in the valence band.
Some electrons are delocalised and free to move through the metal. These electrons are in the conduction band.
These electrons move towards the positive terminal if a
potential difference is applied.
Semi-Conductors
The number of charge carriers increases with temperature, so the
resistance decreases with temperature.
Pure semiconductors are called intrinsic conductors.
Conduction is due to the electrons that break free and move from the valence band to the conduction band.
