## 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.

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.

electric fields and resistors tutorials 2010

electric fields and resistors tutorial answers

## ODU Resources

You moaned and I responded. Here are just the notes for the ODU section, no questions to put you off. I will move the questions to the Learning Outcome Booklet.

## Updated for the 2018 changes

Part 1, containing notes, tutorials and practicals

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

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

OUR DYNAMIC UNIVERSE part 2

Well after spending 18 months or more several years ago putting everything together students have unanimously declared they want everything separated, so your wish is my command students- here is the complete Our Dynamic Universe section notes with nothing but the essential practicals plus one!

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.

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

## New for 2022 KNOWLEDGE ORGANISERS

Teamwork by Mr Stewart (Berwickshire HS) and I. He designed and made them and I tweaked them. Thanks Mr Stewart they’re ace!

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

1. 1a Equations of motion

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.

Chapter 1 exam questions B for CFE higher

Chapter 1 exam Answers B for CFE higher

These are powerpoints prepared for the Revised Higher in 2000. They are still relevant now, and talk through example questions. They are great for revision.

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!

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

A lovely little summary from G Gibb!

## Equations of Motion

4.4 ODU EqoM 2012 this document has the macros enabled (actually I think you might need to contact me to get the macros, they are not allowed to be uploaded on a WordPress Website. It allows you to check your answers for the acceleration time graphs that you drew from the velocity time graph diagrams.

using displacement equation to prove the last equation

## Momentum

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

## Gravitation

Projectiles thanks to Mr. Rossi for this one.

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

## Special Relativity

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.

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

## The Expanding Universe

The expanding universe powerpoints. Might not be quite the final version

Are we missing something in the Expanding Universe?

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

# 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.

## Higher Past Papers

These papers and marking instructions are reproduced to support SQA qualifications, please check the conditions of use and ensure they are not used for commercial benefit.

## National Qualification Higher Physics Papers

Digital Paper
(spell)
Higher
Paper
YEARMIExam
Report
2022 H P2

2022 H P1
2022
NO EXAMNO EXAM2020COVID-19FOR THE 1ST TIME IN ITS HISTORY
NH 20192019mi H 20192019 Report
NH SpecP1
NH Spec P2
SpecMI H P1
MI H P2
2018 DQPNH 20182018MI H 20182018 Report
2017 DQPNH 20172017MI H 20172017 Report
2016 DQPNH 20162016MI H 20162016 Report
2015 DQPNH 20152015MI H 20152015 Report
H S1 DQP
H S2 DQP
NH SpecSpecMI H Spec
Physics
marking
general
principles
THIS!
MARK GUIDE

If you’d like to work through past papers by topic then Mr Davie has done all the hard work for you and has promised to keep this list up to date. He says

http://bit.ly/HigherPhysics18

Below are the Revised Higher Past Papers, the content is very very similar to the new National (CfE) Higher, although the marks would be different. These were the last past papers with half marks!

Higher
Paper
YEARMIExam Feedback
H Rev 20152015MI Rev 20152015 Report
H Rev 20142014MI Rev 20142014 Report
H Rev 20132013MI Rev 2013
2013 Report
H Rev 20122012MI Rev 20122012 Report
H Rev SpecSpecimen
Paper
MI Rev Spec
THIS
MARK GUIDE

These are the traditional Higher Past Papers (once also known as revised!) Remember some of this material is no longer on the syllabus, and some is relevant to National 5.

Higher
Paper
YEARMarking
Instructions
Exam
Feedback
H 20152015MI 20152015 Report
H 20142014MI 20142014 Report
H 20132013MI 20132013 Report
H 20122012MI 20122012 Report
H 20112011MI 20112011 Report
H 20102010MI 20102010 Report
H 20092009MI 20092009 Report
H 2008 2008MI 20082008 Report
H 20072007MI 20072007 Report
H 20062006MI 20062006mcH&Int2 stats2006 Report
H 20052005MI 20052005 Report
H 20042004MI 20042004 Report
H 20032003MI 20032003 Report
H 20022002MI 20022002 Report
H 20012001MI 20012001 Report
H 20002000MI 2000
Internal report

U Standards 2000
H Rev Specimen QPSpecimenMI H Rev Specimen

From National Parent Forum of Scotland This great little pdf file gives some ideas of suitable questions from the traditional Higher papers that are suitable for the new National Qualifications.

Thanks to Mr John Irvine and Mr Stuart Farmer for the course reports.

PLEASE both teachers and students READ the Report after tackling the past paper. The course reports give really good background and information about how candidates performed in the exam and what messages you should learn from them.

Higher
Paper
YEARMarking
Instructions
1999H 1999 PI Solutions
H 1999 PII Solutions
1998H 1998 PI Solutions
H 1998 PII Solutions
1997H 1997 PI Solutions
H 1997 PII Solutions
1996H 1996 P1 Solutions
H 1996 PII solutions
1995H 1995 PI Solutions
H 1995 PII Solutions
1994H 1994 PI Solutions
H 1994 PII Solutions
1993H 1993 PI Solutions
H 1993 PII Solutions
1992H 1992 PI solutions
H 1992 PII Solutions
1991

All the best with your revision!