Electricity Flashcards
What is E.M.F
The E.M.F is the energy that is given to each coulomb of charge as it passes through a supply
Conductors - Electrical Properties
Materials with many free electrons. These electrons can easily be made to flow through the material.
Examples: all metals, semi-metals like carbon- graphite, antimony and arsenic.
Insulator - Electrical Properties
Materials that have very few free electrons.
Examples: plastic, glass and wood
Semi conductors - Electrical Properties
Materials that behave like insulators when pure, but will conduct when an impurity is added and/or in response to light, heat, voltage etc.
Examples: Elements: silicon, germanium, selenium
Band Theory - conductors
There is no energy/band gap
in some metals, the valence band and conduction bands overlap.
The conduction band is only partially filled which means that there are spaces for electrons to travel into from the valence band.
When electrons in the valence band move into the conduction band, they are free to move and this allows conduction to take place.
Band Theory - Insulators
In an insulator, the valence band is full & the conduction band is empty.
The energy/band gap in an insulator is very large.
The energy/band gap is much too large for any electrons in the valance band to make the jump to the conduction band.
As a result, no conduction can take place with an insulator.
Band Theory - Semiconductors
The band gap (between the valence and conduction bands) is small
Some electrons have enough energy to move from the valence to the conduction band
