Semiconductors

For some of you this first link will help explain about semiconductors, for others it will freak you out. If you are someone who likes to know and understand the background behind your Physics, then this video will help in your understanding. If you just like to accept what you’ve been taught then maybe give it a wide berth! It explains where these energy gaps come from, what is means to be a semi-conductor. The SSERC meet mentions the words “quantum tunnelling” which appears in AH Physics. If keeping up with the basics is enough then use the hour for more useful revision.  I am 29 mins in, and it has taken my 40 mins, but it is very informative.

Remind you of anyone? Continue reading “Semiconductors”

Electricity Resources

Electricity Part 1_28 Word document for part one of the Electricity Course. You might have trouble accessing this file as it is a macro enabled word document so could claim to contain viruses. It doesn’t! If you have problems download the pdf version, which is much smaller, but can’t be edited. Eventually I’ll sort all the terrible circuit diagrams and add answers, but for now, you’ll have to ask me for the answers. If anyone is bored after exams I can give you the worked answers to type up!

Electricity Part 1_28 this is the pdf version of the document above covering circuits, emf and capacitors.

E&E Part 2_19 Word document for the second part of the Electricity course, covering the wonderful band theory! Sorry to end on this!

E&E Part 2_19 pdf document for the second part of the electricity unit

Power Matching (word)  Power Matching (pdf) Here is a task to show how to get the greatest power from your circuit. I’ve uploaded it as a pdf and word document.

Here are the answers in an excel spreadsheet, but don’t peek until you’ve completed your own graphs and table! power matching

semiconductors working 2

White Board Revision of Electricity 2

final-question-past-paper Here are the questions from the Revised Higher Physics Papers in topic order with the marking instructions. If you can’t read this I can upload as a pdf file, just ask!

A graph of current against time for charging and discharging at different frequencies. Notice how at low frequencies (0-16s) the current can drop quite low, whereas at higher frequencies (16-26s) their is greater current overall.

 Term Definition Intrinsic semiconductor Undoped group 4 semiconductor eg Silicon Extrinsic semiconductor A semiconducing group 4 material with impurities of grp3 or grp5 material n-type semiconductor Crystal lattice of grp 4 semiconductor doped with a small portion of grp 5 material to provide negative charge carriers. Overall zero charge p-type semiconductor Semiconducting material of gp4 with grp 3 impurities which creates a “hole” Doping When very small amounts of impurities are added to the intrinsic semiconductor, this changes the properties of the material. Diode A component made of n-type and p-type material grown together to create (a device that allows current in one direction only) junction Where the n-type and p-type materials are joined, this allows electrons and holes to diffuse across the gap Conductor A solid material that has electrons in the conduction band Insulator A solid material with no electrons in the conduction band and a large energy gap between the valence and conduction bands Valence band The highest occupied band containing electrons. The band containing electrons with the highest energies and still be associated with a particular atom of a solid material. Conduction band The first unfilled band above the valence band, allowing the electron to dissociate from a particular atom and become a free charge carrier in the material.

Here is a nice introduction to semiconductors

Band Theory

2016 Higher Question Paper

Some cars use LEDs in place of filament lamps. An LED is made from semiconductor material that has been doped with impurities to create a p-n junction. The diagram represents the band structure of an LED.

A voltage is applied across an LED so that it is forward biased and emits light.

Using band theory, explain how the LED emits light.

(Voltage applied causes) electrons to move towards conduction band of p-type/ away from n-type (towards the junction) (1)

Electrons move/ drop from conduction band to valence band (1)

Photon emitted (when electron drops) (1)

Anderson High School

higher-ee-teacher-notes-20161222

Thanks to N Hunter for these great notes from Anderson High.

This is the end of the course! Thanks for making the journey with me. Just revision to do now. All of those resources can be found in the REVISION section.