CH 6 Flashcards
(16 cards)
Electrical conductors
Are materials with electrical resistivity less than 10^-3 ohm.cm .
Semiconductors
Are materials with electrical resistivity between 10^-3 and 10^12 ohm.cm. Semiconductors have a low ability to transmit electrical charges at room temperature but will conduct electricity at high temperatures.
Band theory
For electrical conductivity to occur, electrons must move from the valence band into the conduction band.
Intrinsic semiconductors
These are Semiconductors in their purest form as shown in the periodic table.
Extrinsic semiconductor
These are semiconductors in which the width of the band gap is controlled by deliberate addition of impurities.
N-type extrinsic semiconductors
The semiconductor is doped with a dopant with excess electrons.
P-type extrinsic semiconductors
The semiconductor is doped with a dopant with a deficiency of electrons.
Dielectric materials
These are insulators that can be polarised when placed in an electric field.
Ohm’s law
States that the voltage across an electrical conductor is directly proportional to the current flowing through it provided resistance remains constant.
Electrical resistivity
Measures how strongly a material opposes flow of electrical charge through it.
Electrical conductivity
Refers to the ability of a material to allow the flow of electrical charge.
Drift velocity
The rate at which charge carriers move through a material under the influence of an electric field is called drift velocity.
Breakdown phenomenon
When subjected to high voltage, atoms in non-conductors may be ionised, thereby creating free electrons with sufficient energy to move from the valence band to the conduction band.
Dielectric strength
Of a material is thus the maximum voltage it can withstand without experiencing electrical breakdown.
Permittivity
Is the ability of a material to polarise and store electrical charge within it.
Capacitance
Is the ability of a material to store electrical charge.
