Electricity Resources

The 2018 part 1 Electricity Notes.

this is the pdf version of the document above covering a.c/ d.c, rms, resistance, circuits, and emf.  

And even hotter off the press part 2 Electricity Notes, sorry these have taken 6 months!


Remember

An LED is FORWARD biased. A photon is emitted when an electron falls from the conduction band into the valence band.

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.

Here is a nice introduction to semiconductors

Band Theory


TermInformation
ConductorsConductivity is the ability of materials to conduct charge carriers (electrons or positive holes) (all metals, semi metals like carbon-graphite, antimony and arsenic)
Insulators Materials that have very few charge carriers (free electrons or positive holes). (plastic, glass and wood)
Semi-conductors These materials lie between the extremes of good conductors and good insulators. They are crystalline materials that are insulators when pure but will conduct when an impurity is added and/or in response to light, heat, voltage, etc (silicon (Si), germanium (Ge), gallium arsenide (GaAs)
Band structure Electrons in an isolated atom occupy discrete energy levels. When atoms are close to each other these electrons can use the energy levels of their neighbours. When the atoms are all regularly arranged in a crystal lattice of a solid, the energy levels become grouped together in a band. This is a continuous range of allowed energies rather than a single level. There will also be groups of energies that are not allowed, what is known as a band gap. Similar to the energy levels of an individual atom, the electrons will fill the lower bands first. The fermi level gives a rough idea of which levels electrons will generally fill up to, but there will always be some electrons with individual energies above this
In a conductor: the highest occupied band, known as the conduction band, is not completely full. This allows the electrons to move in and out from neighbouring atoms and therefore conduct easily
In an insulator: the highest occupied band is full. This is called the valnce band, by analogy with the valence electrons of an individual atom. The first unfilled band above the valence band above the valence band is the conduction band. For an insulator the gap between the valence and conduction bands is large and at room temperature there is not enough energy available to move electrons from the valence band into the conduction band, where they would be able to contribute to conduction. Normally, there is almost no electrical conduction in an insulator. If the applied voltage is high enough (beyond the breakdown voltage) sufficient electrons can be lifted to the conduction band to allow current to flow. Often this flow of current causes permanent damage. Within a gas this voltage is often referred to as the striking voltage, particularly within the context of a fluorescent lamp since this is the voltage at which the gas will start to conduct and the lamp will light.
In a semi-conductor: the gap between the valence band and the conduction band is smaller, and at room temperature there is sufficient energy available to move some electrons from the valence band into the conduction band, allowing some conduction to take place. An increase in temperature increases the conductivity of the semiconductor as more electrons have enough energy to make the jump to the conduction band. This is the basis of an NTC thermistor. NTC stands for "negative temperature coefficient" (increased temperature means reduced resistance). This makes current increase so conductivity increases.
Optical properties of materials Electron bands also control the optical properties of materials. They explain why a hot solid can emit a continuous spectrum rather than a discrete spectrum as emitted by a hot gas. In the solid the atoms are close enough together to form continuous bands. The exact energies available in these bands also control at which frequencies a material will absorb or transmit and therefore what colour will appear
Bonding in semi-conductors The most commonly used semiconductors are silicon and germanium. Both these materials have a valency of 4 (they have 4 outer electrons available for bonding. In a pure crystal, each atom is bonded covalently to another 4 atoms: all of its outer electrons are bonded and therefore there are few free electrons available to conduct. This makes resistance very large. Such pure crystals are known as intrinsic semiconductors. The few electrons that are available come from imperfections in the crystal lattice and thermal ionisation due to heating. A higher temperature will thus result in more free electrons, increasing the conductivity and decreasing the resistance, as in a thermistor
Doping Semiconductor's electrical properties are dramatically changed by the addition of very small amounts of impurities. Once doped the semiconductors are known as extrinsic semiconductors. OR Doping a semiconductor involves growing impurities such as boron or arsenic into an intrinsic semiconductor such as silicon
An intrinsic semi-conductor is an undoped semiconductor
Fermi level Energy of latest occupied level in which the states below this energy are completely occupied and above it are completely unoccupied
N-type semi-conductors If an impurity such as arsenic with 5 outer electrons is present in the crystal lattice then 4 of its electrons will be used in bonding with the silicon. The 5th will be free to move about and conduct. Since the ability of the crystal to conduct is increased, the resistance of the semiconductor is therefore reduced. Because of the extra electrons present, the Fermi level is closer to the conduction band than in an intrinsic semiconductor. This type of conductor is called n - type, since most conduction is by the movement of free electrons (-ve)
P-type semi-conductors The semiconductor may also be doped with an element like Indium, which has 3 outer electrons. This produces a hole in the crystal lattice, where an electron is "missing". Because of this lack of electrons, the Fermi level is closer to the valence band than in an intrinsic semiconductor. An electron from the next atom can move into the hole created, as described previously. Conduction can thus take place by the movement of positive holes. Most conduction takes place by the movement of positively charged holes
Notes on doping The doping material cannot be added to the semiconductor crystal. It has to be grown into the lattice when the crystal is grown so that it becomes part of the atomic lattice.
ImpuritiesThe quantity of the impurity is extremely small (could be 1 atom in 1 million). If it were too large it would disturb the regular crystal lattice.
Semi-conductor ChargeOverall charge on semiconductors are still neutral
Minority charge carriersIn n - type and p - type there will always be small numbers of the other type of charge carrier, known as minority charge carriers, due to thermal ionisation.
p-n junctions When a semiconductor is grown so that 1 half is p-type and 1 half is n-type, the product is called a p-n junction and it functions as a diode. A diode is a discrete component that allows current to flow in one direction only.
@ T greater than Absolute ZeroAt temperatures other than absolute Zero kelvin, the electrons in the n-type and the holes in the p-type material will constantly
diffuse(particles will spread from high concentration regions to low concentration regions). Those near the junction will be able to diffuse across it.
Reverse-biased Cell connected negative end to p-type and positive end to n-type
Forward-biased Cell connected positive end to p-type and negative end to n-type.
Reverse biased - charge carriers When the p-side is attached to the negative side of a battery then the electrons at that side have more potential energy than previously. This has the effect of raising the bands on the p-side from where they were originally. We say it is reverse-biased. Almost no conduction can take place since the battery is trying to make electrons flow "up the slope" of the difference in conduction bands. The holes face a similar problem in flowing in the opposite direction. The tiny current that does flow is termed reverse leakage current and comes from the few electrons which have enough energy from the thermal ionisation to make it up the barrier.
Forward biased - charge carriers When the p-side is attached to the positive side of the battery then the electrons at that side have less potential energy than under no bias. This has the effect of lowering the bands on the p-side from where they were originally. We say it is forward biased. As the applied voltage approaches the switching voltage, more electrons will have sufficient energy to flow up the now smaller barrier and an appreciable current will be detected. Once the applied voltage reaches the set voltage there is no potential barrier and the p-n junction has almost no resistance, like a conductor.
In the junction region of a forward-biased LED electrons move from the conduction band to the valence band to emit photons.
The colour of light emitted from an LED depends on On the elements and relative quantities of the three constituent materials. The higher the recombination energy the higher the frequency of light.
The LED does not work in reverse bias since the charge carriers do not/can not travel across the junction towards each other so cannot recombine
Photodiode A p-n junction in a transparent coating will react to light in what is called the photovoltaic effect. Each individual photon that is incident on the junction has its energy absorbed, assuming the energy is larger than the band gap. In the p-type material this will create excess electrons in the conduction band and in the n-type material it will create excess holes in the valence band. Some of these charge carriers will then diffuse to the junction and be swept across the built-in electric field of the junction. The light has supplied energy to the circuit, enabling current to flow (it is the emf in the circuit). More intense light (more photons) will lead to more electron-hole pairs being produced and therefore a higher current. Current is proportional to light intensity.
Photodiode 2The incoming light provides energy for an electron within the valence band of the p-type to be removed from a positive hole and moved up to the conduction band in the n-type material. As this electron is moved up into the conduction band it has an increase in energy. Since EMF is the energy per coulomb of charge an EMF is generated.
Photovoltaic mode The p-n junction can supply power to a load (motor). Many photo-diodes connected together form a solar cell. This is described as photovoltaic mode.There is no bias applied to a solar cell and it acts like an LED in reverse. The increased movement of charge across a p-n junction can reduce resistance of component containing the junction .
Photoconductive mode When connected to a power supply a photodiode will act as a LDR. This is described as photoconductive mode. The LDR is connected in reverse bias, which leads to a large depletion region. When light hits the junction, electrons and holes are split apart. This leads to free charge carriers in the depletion region. The free charge carriers reduce overall resistance of the diode, allowing current to flow. Conductivity of diode is being changed.
ResistanceWhat is decrease by the addition of impurity atoms to a pure semiconductor(doping)
Applications of p-n junctions Photovoltaic cell /LED /Photoconductive mode(LDR)
What is photo-voltaic effect? A process in which a photovoltaic cell converts photons of light into electricity.
How light is produced at the p-n junction of an LED When the diode is forward biased the free electrons in the conduction band of the n-type material are given energy by the supply to overcome the energy barrier generated by the depletion layer at the junction. Once these electrons overcome the energy barrier they drop down from the conduction band to the valence band of the p-type material and combine with a positive hole in the valence band of the p-type material. As the electron drops between the bands it loses energy and emits this as light.
Explain band theoryUse band theory to explain how electrical conduction takes place in a pure semiconductor such as silicon. Your explanation should include the terms: electrons, valence band and conduction band. most/majority of electrons in valence band (½) or "fewer electrons in conduction band" (½) band gap is small electrons are excited to conduction band (½) charge can flow when electrons are in conduction band (½)
Electrons What charge carriers actually move across the p-n junction?

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

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.

Worked Answers

For speed I will add some of the worked answer files here until I can produce an answer booklet, which I’ll do a.s.a.p.

capacitance tutorial answers

electric fields and resistors tutorials 2010

ac voltage tutorials answers corrected

electric fields and resistors tutorial answers

Signature

ODU Resources

These need a real sort out and I’ll get on to it as soon as I can. I’ll upload lots of resources that are now hard to find. I hope they’re useful to teachers and students.

2018-updated

These are part 1 of the notes in pdf format, so you all ought to be able to open them. There is a word version underneath.

OUR DYNAMIC UNIVERSE 2018 pdf

OUR DYNAMIC UNIVERSE 2018 word

These are part 1 of the notes in word format, you can adapt these if you can open them.

For those having trouble with Unit 1 part 1 try this little document

1. 1a Equations of motion

1. 1a Equations of motion

Part 2 still has to be updated to be 2018 ready.

These are part 2 of the notes in word format, you can adapt these if you can open them.

OUR DYNAMIC UNIVERSE part 2 These are part 2 of the notes in pdf format, so you all ought to be able to open them.

I’ve removed the Time Dilation detailed version and added it as a separate document as I suspect most of you wont read them; which is a pity as it makes everything seem fine! Based on Russell Stannard’s excellent book “Relativity- a very short introduction” Oxford. (2008)  ISBN 978–0–19–923622–0)

ODU worked ANSWERS_4 Currently the most up to date version of the worked answers.

ODU worked ANSWERS_4 The pdf version of the most up to date version of the worked answers.

Additional Support

I’ll get corrections up as soon as possible, just a bit hard to get it all done.

For those struggling with the vectors try these to give you some practice Great Resource from Mr Crookes. Set up your 2 vectors, either use a scale diagram or components and compare to the given answer. Enjoy!

AH (Doppler)– some of this is relevant to Higher.

africanfastfood This is an introduction to the momentum topic; think about the collision and where the energy is transferred.

4.4 ODU EqoM 2012 this document has the macros enabled. It allows you to check your answers for the acceleration time graphs that you drew from the velocity time graph diagrams.

If you don’t like proving v2=u2+2as from v=u+at then use this neat little sheet from Mr Mackenzie.

using displacement equation to prove the last equation

Collisions- Think Safety before buying a car!

Relativity

Time dilation02

Cleonis [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0/)]

The green dots and red dots in the animation represent spaceships. The ships of the green fleet have no velocity relative to each other, so for the clocks onboard of the individual ships, the same amount of time elapses relative to each other, and they can set up a procedure to maintain a synchronized standard fleet time. The ships of the “red fleet” are moving with a velocity of 0.866 of the speed of light with respect to the green fleet.

The blue dots represent pulses of light. One cycle of light-pulses between two green ships takes two seconds of “green time”, one second for each leg.

{\displaystyle {\sqrt {3}}}

As seen from the perspective of the reds, the transit time of the light pulses they exchange among each other is one second of “red time” for each leg. As seen from the perspective of the greens, the red ships’ cycle of exchanging light pulses travels a diagonal path that is two light-seconds long. (As seen from the green perspective the reds travel 1.73 ({\displaystyle {\sqrt {3}}}) light-seconds of distance for every two seconds of green time.)The animation cycles between the green perspective and the red perspective, to emphasize the symmetry.

OnVelocities This is a document referred to in the Research Task in the ODU part 2 notes.

PHYSICS WORLD ARTICLE DECEMBER 2009 This is a document referred to in the Research Task in ODU part 2 notes

Projectiles thanks to Mr. Rossi for this one.

Battleships & AWACS Projectiles thanks to Mr. Rossi for this one too.

Chapter 1 exam questions B for CFE higher

Chapter 1 exam Answers B for CFE higher

The Expanding Universe

Are we missing something in the Expanding Universe?

HOMEWORK

The homework booklets are now in the HOMEWORK section.

Homework Booklet Complete pp6-8 (first question), 10-16, 18. Complete notes on Units prefixes and Sci Notation, Uncertainties, Equations of Motion. Read up on Forces.

Updated August 2019
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Particles and Waves Resources

Powers of Ten- this was high tech when I was at school!

Since then a few things have moved on, not least with the physics as well as the graphics.

Orders of Magnitude

The class of scale or magnitude of any amount, where each class contains values of a fixed ratio (most often 10) to the class preceding it. For example, something that is 2 orders of magnitude larger is 100 times larger; something that is 3 orders of magnitude larger is 1000 times larger; and something that is 6 orders of magnitude larger is one million times larger, because 102 = 100, 103 = 1000, and 106 = one million

In its most common usage, the amount scaled is 10, and the scale is the exponent applied to this amount (therefore, to be an order of magnitude greater is to be 10 times, or 10 to the power of 1, greater).

Orders of magnitude are generally used to make very approximate comparisons and reflect very large differences. If two numbers differ by one order of magnitude, one is about ten times larger than the other. If they differ by two orders of magnitude, they differ by a factor of about 100. Two numbers of the same order of magnitude have roughly the same scale — the larger value is less than ten times the smaller value.

Source: Boundless. “Order of Magnitude Calculations.” Boundless Physics Boundless, 26 May. 2016. Retrieved 23 Jan. 2017 from https://www.boundless.com/physics/textbooks/boundless-physics-textbook/the-basics-of-physics-1/significant-figures-and-order-of-magnitude-33/order-of-magnitude-calculations-203-6080/

A proton is 3 orders of magnitude larger than a positron or electron.

Below are the updated 2019 versions. Currently the book is divided into the Standard Model, Forces and Particles and Nuclear Radiation in Part 1 and the waves part will be in part 2, which I have yet to finalise. If you want a colour copy, then you’re welcome to print it out at your own cost.on

P&W ANSWERS Now most of the notes are complete I can start working through the answers. I have got these in a jotter, but will plod through them as quick as I can. They are very slow to type up in equation editor.

…and finally the Particles and Waves book 2 is finished.

Introduction to Particle Physics

The following two documents are a wonderful summary of the Particles and Waves topic from the Revised Higher course courtesy of George Watson’s College, which is very much the current CfE Higher Course.

Particles & Waves

Here’s a lovely little revision sheet on the Standard Model thanks to Mr Ian Cameron.

Standard Model IC word version

Standard Model IC pdf version

particleadventure.org/

Other resources

Orders of magnitude cut out base

quantum model of atom

quantum model of atom answers

Sorting the Fundamental Particles

Standard Model Street

Standard Model Tweet

Tokamak-Energy-Leaflet

atomic-timekeeping-poster

quantum model of atom Mrs Physics’ model of energy level, to help you remember, not necessarily to teach you Physics!

quantum model of atom answers Mrs Physics’ model of energy level answers. Don’t look at these until you’ve tried them yourself!

How to tell a MESON from a BARYON (Stewart, K (2017))

MESON- two syllables = 2 quarks (a quark and antiquark pair)

BARYON- three syllables = 3 quarks

These are the tweets from the higher class this 2017. Describe in under 140 characters the following words. Let us know if you can do better. Some of the tweets are a little over as there are no symbols in wordpress that I can find.
TERMDEFINITION (140 characters or less)
#4 FUNDAMENTAL FORCESFundamental forces: interactions that cannot be reduced. There are 4 types. The forces keep all matter together in the universe.
#ANNIHALATEProcess in which a particle and antiparticle unite, annihilate each other, and produce 1 or more photons. Energy and momentum are conserved.
#ANTIMATTERMatter consisting of elementary particles which are the antiparticles of those making up normal matter.
#BARYONA subatomic particle which has a mass greater than or equal to that of a proton.
#BOSONA subatomic particle, such as a photon, which has zero or integral spin. All the force carrier particles are bosons.
#COLOUR Particle has 3 apparently identical quarks but have different properties categorised by colour to satisfy Pauli Exclusion Principle
#ELECTROMAGNETIC FORCE1 of 4 fundamental forces. influencing electrically charged particles. Responsible for electricity, magnetism and light and holds p+ and e- together
#ELECTROMAGNETIC FORCEAffects electrically charged particles. Responsible for electricity, magnetism, & light;holds e- and p+ in atoms; allows atoms to bond to form molecules. Causes objects to be solid
#EXCHANGE PARTICLEParticle that carries forces for strong force – gluon, weak force – W and Z bosons, electromagnetic – photon and gravitational – graviton.
#FERMIONMatter particles e.g. proton, neutron and electron that have a half-integer spin and are constrained by the Pauli Exclusion Principle.
#GLUONA supposed massless subatomic particle believed to transmit the force binding quarks together in a hadron. They mediate the strong force.
#GRAVITATIONAL FORCEA force that attracts any object with mass.
#HADRONA particle made of quarks. Two families: baryons – made of 3 quarks & mesons – made of 1 quark & 1 antiquark. Protons & neutrons are baryons
#HIGGS BOSONfundamental particle, used by Higgs Field, to interact with other particles two give them m, causes particles to slow therefore cannot reach c due to m.
#LEPTONElementary particles, the basic building blocks of matter. Six leptons are in present structure. Varieties are called flavours.
#MESON Are intermediate mass particles that are made of a quark- antiquark pair. Mesons are bosons and could be hadrons.
#MUONA particle similar to the electron, with an electric charge of −1 e and a spin of 1/2, but with a much greater mass. It is classified as a lepton.
#NEUTRINOA neutral subatomic particle. Mass close to zero. Half-integral spin.Rarely reacts with normal matter. 3 types of neutrino are electron, muon and tau.
#POSITRONPositron= antielectron =the antiparticle of the electron has an. Its electric charge is +1 e, a spin of 1/2, same mass as an electron.
#QUARKQuark: a fundamental particle. Quarks combine to form composite particles called hadrons. The most stable hadrons are protons and neutrons.
#SPINAll particles have spin. Can be up or down & has a fixed value which depends on the type of particle. Particles can be right or left handed
#STANDARD MODELTheory concerning electromagnetic, gravitational, strong and weak nuclear interactions and classifying all known subatomic particles.
#STRONG FORCEBinds quarks together to make subatomic particles e.g.protons and neutrons. Holds together the atomic nucleus. Causes interactions between particles that have quarks.
#WEAK FORCEA force that plays a role in things falling apart, or decaying.

Mrs Physics was given a tweet to do too. I think she did very well, exactly 140 characters with spaces!

#Higgs Boson

= fundamental particle, used by HiggsField 2 interact with other particles 2 give them m, causes particles to slow, \cannot reach c due to m.

\=therefore sign but I haven’t found how to get that yet!

Prof Aidan Robson (Glasgow University)
Hope no one gets to this stage!

It is not as Mrs B said Mrs H’s Bohring Model, but it is more like a Stewart method of remembering the Bohr model!

quantum model of atom

quantum model of atom answers

Photomultipliers- what the heck are they?

https://study.com/academy/lesson/how-photomultiplier-tubes-array-detectors-work.html

Simulations

Here are three links to some cracking simulations for this topic

https://www.cabrillo.edu/~jmccullough/Applets/Applets_by_Topic/Superposition_Interference.html

http://galileoandeinstein.physics.virginia.edu/more_stuff/Applets/rutherford/rutherford2.html

http://science.sbcc.edu/physics/flash/siliconsolarcell/bohratom.swf

PhET Interactive Simulations
University of Colorado Boulder
https://phet.colorado.edu

>

https://phet.colorado.edu/en/simulation/rutherford-scattering

Anderson High school Shetland Notes

With grateful thanks to Ms Nancy Hunter from Anderson High School in Shetland. Apparently these have been voted as the best Higher notes.

pw-booklet-1-teacher-20161212

pw-booklet-2-teacher-20161212

Online simulations

There is a great simulation from Phet Colorado Physics. It is fantastic and we must support this great site.

https://phet.colorado.edu/en/simulation/photoelectric

PhET Interactive Simulations
University of Colorado Boulder
https://phet.colorado.edu

Photoelectric Effect

 
Click to Run

This is a great little introduction to Chapter 7 Interference and Diffraction.

 

A great poster from NPL- measurements are in their care! The poster shows how time keeping has got more and more precise.

Scholar Notes

hg_cphy_Unit2

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Updated February 2019