ENG1002 Lecture Notes - Lecture 7: Electronic Band Structure
30 May 2018
School
Department
Course
Professor
Colour&in&materials:
Metals
When&yellow&light&shone&on&copper,&most&of&the&incident&light&energy&
is&absorbed&due&to&the&electronic&band&structure,&and&re-emitted&from&
the&surface&of&the&material&by&reflection.
Semiconductor
Wavelengths&of&light&selectively&absorbed&through&excitation&of&
electrons&over&the&bandgap&of&width&1.8-3.1eV.&These&electrons&then&
decay&back&to&ground&state,&emitting&photons&in&the&visible&spectrum&
that&appear&as&yellow&light.
Problem&Sheet:
Find&KCL&@&nodes&v1&and&v2
Relatinoship&between&v1&and&v2
Thevenin&and&Norton's:
Voc&-->&KCL&@&one&node,&ground&node&@&the&other
Isc&-->&introduce&wire/short&circuit&between&two&nodes,&&ground&node&the&one&
current&flowing&into
**&both&nodes&must&now&be&0V&because&(connected&to)&ground&node
KCL
Calculate&resistance&using&these&two
**If&no&dependent&sources&(triangle&shaped&sources)&in&circuit,&shortcut:
Zero&all&the&independent&sources&-->&replace&Vsource&with&short circuit,&
replace&Isource&with&open circuit
V&-short;&I&-open&(opposite&of&usually)
All&grounds&are&the&same&node
When the switch is open, there is no path for current to flow in series circuit, so there
is no voltage drop across the resistors, so Voc = original voltage of source
When the switch is closed, the only available current path is through R2 and the
switch. There is still no path for current through R1. The potential between the
resistors is now 0V, and as no current flows through R1, the voltages on either side of
the resistor must be the same. Therefore, the voltage across AB is now also 0V.
Week$7
Tuesday,& 25&April&2017
15:59
