4A.6 Flashcards
what is a semiconductor
they are materials that have a lower resistivity than insulators, but a higher resistivity than conductors, they usually have a small number of delocalized electrons that are free to conduct
how are energy bands formed
in a solid material when many many atoms are close together the energies levels of electrons allowed become much wider, forming an energy band that was a wide range of electron energies
what is a valence band
a range of energy amounts that electrons in a solid material can have which keeps them close to one particular atom
what is a conduction band
a range of energy amounts that electrons in a solid material can have which delocalizes them to move freely through a solid
if we increase the temperature of a semiconductor what will happen to the current following through it
it would decrease its resistivity as more electrons elevated to the higher energy level of conduction, allowing more current to flow through, there will also be more resistance resulting in more collisions of the fixed atoms but it isn’t as significant
what is a conduction hole
it is when an electron is elevated from its original atom forming a “hole” in the atom
how is a conduction hole a charge carrier
as the electrons are attracted to the positive direction of the applied voltage the hole would be moving in the opposite direction forming another current in the semiconductor
how is a diode made
it is made by joining different parts of a semiconductor
because the diode is made of many semiconductors what forms between them
an energy barrier
how does the energy barrier affect the charge carriers in a diode
it blocks their movement
how does the energy charge get past the energy barrier
the charge carriers get past the energy barrier in the forward direction once a small forward voltage is applied
and in the reverse direction is when a large enough amount of reverse voltage is applied to force conduction in the opposite direction
what is a leakage current in a diode
it is when a small number of charge carriers pass through the energy barrier at a low reverse voltage supply
why does an LDRS have less resistance in light
The LDRS are made from semiconductors when light is pointed on it will boost the electrons from their valence energy band to a conduction band
what are LDRS
they are resistors that are made from semiconductors and depend on the light level around them
why do Thermistors have less resistance in heat
thermistors are made from semiconductors, the thermal energy supplied would elevate the electrons in the valance energy band to a conduction energy band
