a level physics notes aqa

8/11/2019 A Level Physics Notes AQA

1/93

AS Physics

Unit 1

Particles, Quantum Phenomena and

Electricity

1 Constituents of the Atom

2 Particles and Antiparticles

3 Quarks

4 Hadrons

5 Leptons

!orces and "#chan$e Particles

% &he Stron$ 'nteraction

( &he )eak 'nteraction

* !eynman +ia$rams

1, &he Photoelectric "-ect

11 "#citation. 'onisation and "ner$y Le/els

12 )a/e Particle +uality

13 Q0't

14 hms La and '0 6raphs

15 esisti/ity and Superconducti/ity

1 Series and Parallel Circuits

1% "ner$y and Poer

1( "7! and 'nternal esistance

1* 8irchho- and Potential +i/iders

2, Alternatin$ Current

21 &he scilloscope

Unit 2

Mechanics, Materials and Waves

1 Scalars and 0ectors

2 esol/in$ 0ectors

3 7oments

4 0elocity and Acceleration

5 7otion 6raphs

"9uations of 7otion

% &erminal 0elocity and Pro:ectiles

( ;etons Las

* )ork. "ner$y and Poer

1, Conser/ation of "ner$y

11 Hookes La

12 Stress and Strain

13


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Ions (Also seen in GCSE Physics 2)An atom may $ain or lose electronsB )hen this happens the atoms @ecomes electricallychar$ed Gpositi/ely or ne$ati/elyIB )e call this an ionB'f the atom $ains an electron there are more ne$ati/e char$es than positi/e. so the atomis a ne$ati/e ionB

6ainin$ one electron ould mean it has an o/erall char$e of 1. hich actually means1B # 1,1*CB

6ainin$ to electrons ould mean it has an o/erall char$e of 2. hich actually means3B2 # 1,1*CB

'f the atom loses an electron there are more positi/e char$es than ne$ati/e. so the atomis a positi/e ionB

Losin$ one electron ould mean it has an o/erall char$e of 1. hich actually means1B # 1,1*CB

Losin$ to electrons ould mean it has an o/erall char$e of 2. hich actually means3B2 # 1,1*CB

?nit 1

Particles and AntiparticlesLesson 2Learnin$

utcomes

&o kno hat is the di-erence @eteen particles and antiparticles

&o @e a@le to e#plain hat annihilation is

&o @e a@le to e#plain hat pair production is ;B +)="

Antimatter


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Pion.ero

Charge(Q)

#aryon$um%er

(#)

&trangeness(&)

Pion.ero

Charge(Q)

#aryon$um%er

(#)

&trangeness(&)

u V T , d T T ,

W V T , dU T T ,

- -

/aonPlus

Charge(Q)

#aryon

$um%er(#)

&trangen

ess(&)

/aonMinus

Charge(Q)

#aryon

$um%er(#)

&trangene

ss(&)

u V T , W V T ,

sU T T 1 s T T 1

/+ +1 +1 / 1 1

/aon.ero

Charge(Q)

#aryon$um%er

(#)

&trangeness(&)

'nti/aon

.eroCharge

(Q)

#aryon$um%er

(#)

&trangeness(&)

d T T , dU T T ,

sU T T 1 s T T 1

/ +1 / 0 1

Anti HadronsAnti hadrons are made from the opposite 9uarks as their Hadron counterparts. fore#ample a proton is made from the 9uark com@ination uud and an antiproton is madefrom the com@ination WWdU

)e can see that a Yand a Yare particle and antiparticle of each otherB'nti

Proton

Charge(Q)

#aryon$um%er

(#)

&trangeness(&)

'nti$eutr

onCharge

(Q)

#aryon$um%er

(#)

&trangeness(&)

W V T , dU T T ,

W V T , W V T ,

dU T T , dU T T ,

*00 1 1 n0 1 =ou need to kno all the 9uark com@ination shon on this pa$e as they may ask you to recite

any of themB

?nit 1

LeptonsLesson 5Learnin$

utcomes

&o @e a@le to e#plain hat a lepton is

&o kno the properties common to all leptons

&o @e a@le to e#plain the conser/ation las and @e a@le to use them ;B +)="

&undamental ParticlesA fundamental particle is a particle hich is not made of anythin$ smallerB


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e*tonCharg

e(Q)

e*ton$um%er

()'nti e*ton

Charge(Q)

e*ton$um%er

()

"lectron e 1 1 Anti "lectron e 1 1"lectron;eutrino Ze , 1

Anti "lectron;eutrino ZUe , 1

7uon [ 1 1 Anti 7uon [ 1 1

7uon ;eutrino Z[ , 1 Anti 7uon ;eutrino ZU[ , 1

&auon \ 1 1 Anti &auon \ 1 1&auon

;eutrino Z\ , 1 Anti &auon ;eutrino ZU\ , 1

Conser'ation #aws!or a particle interaction to occur the folloin$ las must @e o@eyed. if either is /iolatedthe reaction ill ne/er @e o@ser/ed Gill ne/er happenIEChargeE 7ust @e conser/ed Gsame total /alue @efore as the total /alue afterI!aryon "umberE 7ust @e conser/ed#epton "umberE 7ust @e conser/edStrangenessE Conser/ed in "7 and Stron$ 'nteractionB +oesnt ha/e to @e conser/ed in

)eak 'nteraction()amples

'n pair production a photon of ener$y is con/erted into a particle and its antiparticle

] ^ e e

Q , ^ 1 1 , ^ , Conser/ed

< , ^ , , , ^ , Conser/ed

L , ^ 1 1 , ^ , Conser/ed

S , ^ , , , ^ , Conser/edLet us look at @eta plus decay as e kne it at 6CS"B A neutron decays into a proton andreleases an electronB

n ^ p e

Q , ^ 1 1 , ^ , Conser/ed

< 1 ^ 1 , 1 ^ 1 Conser/ed

L , ^ , 1 , ^ 1;otConser/ed

S , ^ , , , ^ , Conser/ed&his contri@uted to the search for and disco/ery of the neutrinoB

Num*er Reminders&here may @e a clue to the char$e of a particle Y. 8and eha/e a positi/e char$eB't ill only ha/e a @aryon num@er if it &a @aryonB 7esons and Leptons ha/e a


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&he $ra/itational interaction causes an attracti/e force @eteen massesB&he stron$ nuclear interaction causes an attracti/e Gor repulsi/eI force @eteen 9uarksGand so hadronsIB

&he eak nuclear interaction does not cause a physical force. it makes particles decayBO)eak means there is a lo pro@a@ility that it ill happenBnteraction"3orce !ange !elative &trength

Stron$ ;uclear M1,15m 1 G1I

"lectroma$netic _ M1,X2 G,B,1I

)eak ;uclear M1,

1(

m M1,

X%

G,B,,,,,,1I6ra/itational _ M1,X3

G,B,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,1I

()change Particles'n 1*35 `apanese physicist Hideki =ukaa put forard the idea that the interactionsforces@eteen to particles ere caused @y O/irtual particles @ein$ e#chan$ed @eteen theto particlesBHe as orkin$ on the stron$ nuclear force hich keeps protons and neutrons to$etherand theorised that they ere e#chan$in$ a particle @ack and forth that Ocarried the forceand kept them to$etherB &his is true of all the fundamental interactionsB

&he $eneral term for e#chan$e particles is bosonsand they are fundamental particles like9uarks and leptonsB

Ice S"ating Analogy'ma$ine to people on ice skates that ill represent the to @odies e#periencin$ a forceB

'f A thros a @olin$ @all to


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Learnin$utcomes

&o kno hy a nucleus doesnt collapse in on itself

&o kno hy the neutron e#ists in the nucleus ;B +)="

The Strong Interaction&he stron$ nuclear force acts @eteen 9uarksB Since Hadrons are the onlyparticles made of 9uarks only they e#perience the stron$ nuclear forceB'n @oth


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Addin$ another protonmeans that all the othernucleons feel the S;!attractionB 't also meansthat all the other protonsfeel the "7 repulsionB

Addin$ another neutron

adds to the S;! attraction@eteen the nucleons @ut. since it isunchar$ed. it does not contri@ute to the "7repulsionB

?nit 1

&he )eak 'nteractionLesson (Learnin$

utcomes

&o @e a@le to rite the e9uation for alpha and @eta decay

&o kno hat a neutrino is and hy is must e#ist

&o @e a@le to state the chan$es in 9uarks durin$ @eta plus and @etaminus decay

;B +)="

Alpha /ecay)hen a nucleus decays in this ay an alpha particle Ga helium nucleusI is e:ected fromthe nucleusB

424

2 + YX

AZ

AZ or HeYX

A

Z

A

Z

4

2

4

2 +

All the emitted alpha particles tra/elled at the same speed. meanin$ they had the sameamount of ener$yB &he la of conser/ation of massener$y is met. the ener$y of thenucleus @efore the decay is the same as the ener$y of the nucleus and alpha particle afterthe decayB

Alpha decay is ;& due to the eak interaction @ut


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+ia$ram 5 represents electron captureB A proton captures an electron and @ecomes aneutron and an electron neutrinoB+ia$ram represents a neutrinoneutron collisionB A neutron a@sor@s a neutrino andforms a proton and an electronB+ia$ram % represents an antineutrinoproton collisionB A proton a@sor@s an antineutrinoand emits a neutron and an electronB+ia$ram ( represents an electronproton collisionB &hey collide and emit a neutron and anelectron neutrinoB

,etting the ()change Particle&he aspect of !eynman dia$rams that students often stru$$le ith is la@ellin$ thee#chan$e particle and the direction to dra itB Look at hat you start ithE'f it is positi/e and @ecomes neutral you can think of it as throin$ aay its positi/echar$e so the @oson ill @e positi/eB &his is the case in electron captureB'f it is positi/e and @ecomes neutral you can think of it as $ainin$ ne$ati/e to neutralise itso the @oson ill @e ne$ati/eB &his is the case in electronproton collisionsB'f it is neutral and @ecomes positi/e e can think of it either as $ainin$ positi/e G)@osonI or losin$ ne$ati/e G)X @oson in the opposite directionIB

-or' out +here the charge is going and label it$

?nit 1

&he Photoelectric "-ectLesson 1,

Learnin$utcomes

&o kno hat the photoelectric e-ect is and ho fre9uency and intensity a-ect it

&o @e a@le to e#plain hat photon. photoelectron. ork function and thresholdfre9uency are

&o @e a@le to calculate the kinetic ener$y of a photoelectron ;B +)="

4*ser'ations)hen li$ht fell onto a metal plate it released electrons from the surface strai$ht aayB'ncreasin$ the intensity increased the num@er of electrons emittedB 'f the fre9uency of theli$ht as loered. no electrons ere emitted at allB 'ncreasin$ the intensity and $i/in$ itmore time did nothin$. no electrons ere emittedBI #ight was a +a'e5'ncreasin$ the intensity ould increase the ener$y of the li$htB &he ener$y from the li$ht

ould @e e/enly spread o/er the metal and each electron ould @e $i/en a small amountof ener$yB "/entually the electron ould ha/e enou$h ener$y to @e remo/ed from themetalB

Photon7a# Planck had the idea that li$ht could @e released in Ochunks or packets of ener$yB"instein named these a/epackets photonsB &he ener$y carried @y a photon is $i/en @ythe e9uationE

hfE= Since fc= e can also rite this asE

hcE=

()plaining the Photoelectric ($ect"instein su$$ested that one photon collides ith one electron in the metal. $i/in$ it

enou$h ener$y to @e remo/ed from the metal and then >y o- somehereB Some of theener$y of the photon is used to @reak the @onds holdin$ the electron in the metal and therest of the ener$y is used @y the electron to mo/e aay Gkinetic ener$yIB He represented

this ith the e9uationE KEhf += hfrepresents the ener$y of the photon. is the ork function and EKis the kinetic ener$yB


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+or" &unction6 &he ork function is the amount of ener$y the electron re9uires to @e completelyremo/ed from the surface of the metalB &his is the ener$y :ust to remo/e it. not to mo/eaayBThreshold &re7uency6 8

&he threshold fre9uency is the minimum fre9uency that ould release an electron fromthe surface of a metal. any less and nothin$ ill happenB

Since KEhf += . the minimum fre9uency releases anelectron that is not mo/in$. so EKJ ,

=0hf hich can @e rearran$ed to $i/eEh

f =0

'ncreasin$ the intensity increases the num@er of photons the li$ht sources $i/es out eachsecondB'f the photon has less ener$y than the ork function an electron can not @e remo/edB'ncreasin$ the intensity :ust sends out more photons. all of hich ould still not ha/eenou$h ener$y to release an electronB

,raph'f e plot a $raph of the kinetic ener$y of the electronsa$ainst fre9uency e $et a $raph that looks like thisE

Start ith KEhf += and transform into cmxy += BEKis the ya#is and fis the # a#isB&his makes the e9uation @ecomeE = hfEKSo the gradient re*resents Planck5s constantand the yinterce*t re*resents (;) the


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The Pro*lem with Atomsutherfords nuclear model of the atom lea/es us itha pro@lemE a char$ed particle emits radiation hen itacceleratesB &his ould mean that the electrons ouldfall into the nucleusB

%ohr to the Rescue;iels


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Learnin$utcomes

&o @e a@le to e#plain hat electron di-raction shos us

&o kno hat a/eparticle duality is ;B +)="

/e %roglie'n 1*23 Louis de


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?nit 1

Q0'tLesson 13Learnin$

utcomes

&o @e a@le to e#plain hat current. char$e. /olta$epotential di-erence andresistance are

&o kno the e9uations that link these

&o kno the correct units to @e use in each ;B +)="

/efnitions (Also seen in GCSE Physics 2)Current6 I"lectrical current is the rate of >o of char$e in a circuitB "lectrons are char$ed particlesthat mo/e around the circuitB So e can think of the electrical current is the rate of the>o of electrons. not so much the speed @ut the num@er of electrons mo/in$ in thecircuitB 'f e ima$ine that electrons are =ear % students and a ire of a circuit is a corridor.the current is ho many students passin$ in a set timeB

Current is measured in 'm*eres (or 'm*s), 'Charge6 !

&he amount of electrical char$e is a fundamental unit. similar to mass and len$th andtimeB !rom the data sheet e can see that the char$e on one electron is actually 1B, #1,1* CB &his means that it takes B25 # 1,1(electrons to transfer 1C of char$eB

Charge is measured in Coulom%s, C9oltage:Potential /i$erence6 9

0olta$e. or potential di-erence. is the ork done per unit char$eB1 unit of char$e is B25 # 1,1(electrons. so e can think of potential di-erence as theener$y $i/en to each of the electrons. or the pushin$ force on the electronsB 't is the pBdBthat causes a current to >o and e can think of it like ater >oin$ in a pipeB 'f e makeone end hi$her than the other end. ater ill >o don in. if e increase the hei$htGincrease the pBdBI e $et more >oin$B 'f e think of current as =ear %s alkin$ don acorridor. the harder e push them don the corridor the more e $et >oin$B

?oltage and *d are measured in ?olts, ?Resistance6 R

&he resistance of a material tells us ho easy or dicult it is to make a current >othrou$h itB 'f e think of current as =ear %s alkin$ don a corridor. it ould @e harder tomake the =ear %s >o if e added some =ear 11 ru$@y players into the corridorB 'ncreasin$resistance loers the currentB

!esistance is measured in @hms, ATime6 t

=ou kno. time Ho lon$ stu- takes and thatBime is measured in seconds, s

(7uations&here are three e9uations that e need to @e a@le to e#plain and su@stitute num@ers intoB

;

t

Q

I

= &his says that the current is the rate of chan$e of char$e per second and @acks up or ideaof current as the rate at hich electrons Gand char$eI >oB

&his can @e rearran$ed intotIQ =

hich means that the char$e is e9ual to ho much is >oin$ multiplied @y ho lon$ it>os forB

o throu$h resistors2 and 3B

&he total current is e9ual to the sum of the currents throu$heach resistorB

321 IIIITOTAL ++=

&he total potential di-erence is e9ual to the pBdBs across each

resistorB

321 VVVVTOTAL ===

&he total resistance can @e calculated usin$ the e9uationE

321

1111

RRRRTOTAL++=


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+ater Slide Analogy'ma$ine instead of $ettin$ a potential di-erence e $et a hei$htdi-erence @y reachin$ the top of a slideB &his series circuit has threeconnected slides and the parallel circuit @elo has three separate slidesthat reach the @ottomB

9oltages:P/s'n series e can see that the total hei$ht loss is e9ual to ho much you

fall on slide 1. slide 2 and slide 3 added to$etherB &his means that thetotal pBdB lost must @e the pBdB $i/en @y the @atteryB 'f the resistors ha/ee9ual /alues this drop in potential di-erence ill @e e9ualB'n parallel e see each slide ill drop @y the same hei$ht meanin$ the potential di-erenceis e9ual to the total potential di-erence of the @atteryB

Currents'f e ima$ine 1,, people on the ater slide. in series ecan see that 1,, people $et to the topB All 1,, must $odon slide 1 then slide 2 and nal slide 3. there is no otheroptionB So the current in a series circuit is the same

e/eryhereB'n parallel e see there is a choice in the slide e takeB 1,,people $et to the top of the slide @ut some may $o donslide 1. some don slide 2 and some don slide 3B &he totalnum@er of people is e9ual to the num@er of people $oin$don each slide added to$ether. and the total current ise9ual to the currents in each circuitloopB

?nit 1

"ner$y and PoerLesson 1%Learnin$

utcomes

&o kno hat poer is and ho to calculate the poer of an electrical circuit

&o kno ho to calculate the ener$y transferred in an electrical circuit

&o @e a@le to deri/e further e9uations or use a series of e9uations tond the anser

;B +)="

Power (Also seen in GCSE Physics 1)Poer is a measure of ho 9uickly somethin$ can transfer ener$yB Poer is linked toener$y @y the e9uationE

Po


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)e can also rearran$e IRV= intoR

VI= and su@stitute this into VIP= to $et our last

e9uation for poerE

VIP= gR

VI= so

R

VP

2

= G4I

(nergy again&o more e9uations for ener$y can @e deri/ed from the e9uation at the top and e9uations3 and 4

"ner$y J Poer # time

RtIPt 2= "9uation 3 @ecomes RtIE 2= G5I

tR

VPt

2

= "9uation 4 @ecomes tR

VE

2

= GI

&uses (Also seen in GCSE Physics 2)"lectrical de/ices connected to the 7ains supply @y a threepin plu$ ha/e a fuse as part oftheir circuitB &his is a thin piece of ire that melts if the current throu$h it e#ceeds itsma#imum toleranceB &he common fuses used are 3A. 5A and 13AB A 1,,) li$ht @ul@connected to the ?8 7ains ould ha/e a 24,0 potential di-erence across itB ?sin$ IVP=e can see that the current ould @e ,B42A so a 2A fuse ould @e the @est to useB

Applications&he starter motor of a motor car needs to transfer a lot of ener$y /ery 9uickly. meanin$its needs a hi$h poerB 7illions of `oules are re9uired in seconds since the /olta$e of the@attery is unchan$in$ e need current in the re$ion of 1,A hich is enormousB

&he poer lines that are held @y pylons and form part of the ;ational 6rid are /ery thickand carry electricity that has a /ery hi$h /olta$eB 'ncreasin$ the /olta$e loers the

current so if e look at the e9uation RtIE 2= e can see that this loers the ener$ytransferred to the surroundin$sB

?nit 1

"7! and 'nternal esistanceLesson 1(Learnin$

utcomes

&o kno hat emf and internal resistance are

&o kno ho to measure internal resistance

&o @e a@le sketch and interpret a 0' $raph. la@ellin$ the $radientand yintercept

;B +)="

(nergy in Circuits'n circuits there are to fundamental types of componentE ener$y giversand ener$y

ta'ersB(lectromoti'e &orce 0em26 B

"ner$y $i/ers pro/ide an electromoti/e force. they force electrons around the circuithich transfer ener$yB

&he sie of the emf can @e calculate usin$EQ

E=

&his is similar to the e9uation e use to nd /olta$epotential di-erence and means theener$y $i/en to each unit of char$eB )e can think of this as the ener$y $i/en to eachelectronBhe em% o% a supply is the p$d$ across its terminals +hen no current 0o+s

EM3 is measured in :oules *er Coulom%, :C1or ?olts, ?

"ner$y takers ha/e a potential di-erence across them. transferrin$ ener$y from the circuitto the componentB

emf J ener$y $i/er pBdB J ener$y taker"ner$y is conser/ed in a circuit so ener$y in J ener$y out. orE

The t"t%l "f the emf& ' The t"t%l "f the p"tenti%l diffeence& %"und the #h"le cicuit


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Internal Resistance6 r&he chemicals inside a cell o-er a resistance to the >o of current. this is the internalresistance on the cellB

nternal !esistance is measured in @hms, A

#in"ing em and r'f e look at the statement in the @o# a@o/e and apply it to the circuit @elo. e canreach an e9uation that links emf and B

&otal emfs J total potential di-erences J GpBdB across rI GpBdB across I

emem@er that 0J' J G' # rI G' # I J 'r '

( ' I)*R+

he terminal p$d$ is the p$d$ across the terminals o% the cell+hen a current is 0o+ing

J internal pBd terminal pBdBSo the a@o/e e9uation can @e ritten as ( ' I * V here Vis theterminal pBdB

Measuring em and r

)e can measure the emf and internal resistance of a cell @ymeasurin$ the current and /olta$e as shon on the ri$ht. the/aria@le resistor allos us to $et a ran$e of /aluesB 'f e plot theresults onto a $raph of /oltmeter readin$ a$ainst ammeterreadin$ e $et a $raph that looks like the one @eloB6raphs ha/e the $eneral e9uation of y J m#c. here y is the/ertical GupardsI a#is. # is the horiontal GacrossI a#is. m is the

$radient of the line and c is herethe line intercepts GcutsI the y a#isB'f e take ( ' I * Vand arran$e it into yJ m# c y a#is J V and # a#is JI ( ' I * V V ' ,I * ( V ' , I * (

y Jm #cSo e can see that theE

yinterce*t re*resents the em=andgradient re*resents (;)internal resistance

?nit 1

8irchho- and Potential

+i/idersLesson 1*

Learnin$utcomes

&o kno 8irchho-s las and @e a@le to apply them to 9uestions

&o kno hat a potential di/iders is and @e a@le to calculate the output /olta$e

&o @e a@le to e#plain an application of a potential di/ider ;B +)="

irchho$>s #aws8irchho- came up ith to Gsome may say rather o@/iousI lasconcernin$ conser/ation in electrical circuitsB

Captain 4*'ious> &irst #aw

"lectric char$e is conser/ed in all circuits. all the char$e thatarri/es at a point must lea/e itBCurrent $oin$ in J current $oin$

outB'n the dia$ram e can say thatE I1' I2* I3 * I4

Captain 4*'ious> Second #aw


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"ner$y is conser/ed in all circuits. for any complete circuit the sum of the emfs is e9ual tothe sum of the potential di-erencesB

"ner$y $i/ers J ener$y takersB'n the dia$ram e can say thatE J pd1 pd2 pd3 pd4B

Potential /i'idersA potential di/ider is used to produce a desiredpotential di-erence. it can @e thou$ht of as a potentialselectorB

A typical potential di/ider consists of to or moreresistors that share the emf from the @atterycellB

&he pBdBs across R1andR2can @e calculated usin$ thefolloin$ e9uationsE

21

1

01RR

RVV

+=

21

2

02RR

RVV

+=

&his actually shos us that the sie of the potential di-erence is e9ual to the inputpotential multiplied @y hat proportion of R1is of the total resistanceB

'fR1is 1, and R2is *, . R1contri@utes a tenth of the total resistance soR1has a tenthof the a/aila@le potentialB &his can @e represented usin$E

2

1

2

1

V

V

R

R= &he ratio of the resistances is e9ual to the ratio of the output /olta$esB

ses'n this potential di/ider the second resistor is a thermistorB )henthe

temperature is lo the resistance GR2I is hi$h. this makes theoutput /olta$e

hi$hB )hen the temperature is hi$h the resistance GR2I is lo. this

makes theoutput /olta$e loB A use of this ould @e a coolin$ fan thatorks harder

hen it is armB

'n the second potential di/ider the second resistor is a Li$ht+ependant esisitorB

)hen the li$ht le/els are lo the resistance GR2I is hi$h.makin$ the output /olta$e

hi$hB )hen the li$ht le/els increase the resistance GR2Idecreases. this makes the

output /olta$e decreaseB A use of this could @e a street li$htsensor that li$hts up

hen the surroundin$ are darkB

?nit 1

Alternatin$ CurrentLesson 2,Learnin$

utcomes

&o kno hat peak current/olta$e is and to @e a@le to identify it

&o kno hat peaktopeak current/olta$e is and to @e a@le to identify it

&o kno hat rBmBsB /alues are and to @e a@le to calculate them ;B +)="

AC/C /efnitions (Also seen in GCSE Physics 2)/irect Current

Cells and @atteries are suppliers of direct current they supply an emf in one directionB


24/93

'n the $raph @elo e can see that the current and /olta$e are constantB &he @ottom lineshos that hen the @attery or cell is re/ersed the /olta$e and current are constants inthe other direction

Alternating Current&he 7ains electricity supplies an alternatin$ current it supplies an emf that alternatesfrom ma#imum in one direction to ma#imum in the other directionB'n the $raph @elo e see the /olta$e and current start at ero. increase to a ma#imum inthe positi/e direction. then fall to ero. reach a ma#imum in the ne$ati/e direction andreturn to eroB &his is one cycleB

Alternating Current /efnitionsPea" 9alue&he peak /alue of either thecurrent or the potential di-erenceis the ma#imum in eitherdirectionB 't can @e measuredfrom the a/e as the amplitude.the distance from , to the top Gor@ottomI of the a/eB )e denotepeak current ith I,and peak pBdBith V,B

Pea"-to-Pea" 9alue

&he peaktopeak /alue of eitherthe current or potential di-erenceis the ran$e of the /aluesB &his is literally the distance from the peak a@o/e the ero lineto the peak @elo the lineB

Time Period'n an aBcB current or pBdB this is the time taken for one complete cycle Gor a/eIB

&re7uencyAs ith its use at 6CS". fre9uency is a measure of ho many complete cycles that occurper secondB

3reBuency is measured in ertD, DRoot Mean S7uared6 rms

Since the current and pBdB is constantly chan$in$ it is impossi@le to assi$n them a #ed/alue o/er a period of time. the a/era$e ould @e eroB &he rBmBsB current produces thesame heatin$ e-ect in a resistor as the e9ui/alent dBcB for e#ample 120 dc J 120rms ac

2

0I

Im& = hich can @e rearran$ed to $i/e 20 m&II =

2

0VVm& = hich can also @e rearran$ed to $i/e 20 m&VV =

?nit 1

&he scilloscopeLesson 21Learnin$

utcomes

&o kno hat are the main controls of the oscilloscope&o @e a@le to determine the /olta$e and current usin$ an oscilloscope

&o @e a@le to determine the time period and fre9uency usin$ anoscilloscope

;B +)="


25/93

The4scilloscope

An oscilloscopecan @e used tosho the sies of/olta$es andcurrents in @othdBcB and aBcBcircuitsB &his is

hat a typicaloscilloscopelooks likeB Atrace ould @eseen on the $rid displayB

/C Traces (Also seen in GCSE Physics 2)'f e connected a @attery or cell to an oscilloscope. e ould see atrace similar to the one shon hereB &he current of a dBcB supply isconstant. this means the /olta$e is constantB

)e see a strai$ht lineB

AC Traces (Also seen in GCSE Physics 2)'f e connect anythin$ that dras poer from the 7ains to anoscilloscope e ill see a similar trace to the one shon hereB &hecurrent is constantly chan$in$ from ma#imum >o in onedirection to ma#imum >o in the other direction this meansthe /olta$e is doin$ the sameB)e see a a/eB

Controls

&here are to main controls that e use are the /oltsdi/ and time @ase dialsE&he /oltsdi/ G/olts per di/isionI dial allos you to chan$e ho much each /ertical s9uareis orthB

&he time @ase dial allos you to chan$e ho much each horiontal s9uare is orthB

9oltage)e can measure the /olta$e of a dBcB supply @y countin$ the num@er or /ertical s9uaresfrom the ori$in to the line and then multiplyin$ it @y the /oltsdi/B 'n the trace the line is2B5 s9uares a@o/e ,. if each s9uare is orth 5 /olts the /olta$e is G2B5 # 5I 12B5 /oltsB)e can measure the peak /olta$e of an aBcB supply @y countin$ ho many /erticals9uares from the centre of the a/e to the top and then multiplyin$ it @y the /oltsdi/Gho much /olta$e each s9uare is orthIB 'n the trace the peak /olta$e is 4 s9uares hi$h.if each s9uare is orth 5 /olts the /olta$e is G4 # 5I 2, /oltsB

Time and &re7uency)e can measure the time for one period Ga/eI @y countin$ ho many horiontal s9uaresone a/elen$th is and then multiplyin$ it @y the time @ase Gho much time each s9uareis orthIB'n the trace a@o/e one a/e is s9uares lon$. if each s9uare is orth ,B,2 seconds thetime for one a/e is ,B12 secondsB)e can calculate the fre9uency Gho many a/es or many times this happens persecondI usin$ the e9uationE

Tf

1

= and fT 1

='f the time period is ,B12 seconds. the fre9uency is (B33H

3reBuency is measured in ertD, D

?nit 2

Scalars and 0ectorsLesson 1


26/93

Learnin$utcomes

&o kno the di-erence @eteen scalars and /ectors and @e a@le to list somee#amples of each

&o @e a@le to add /ectors @y scale drain$

&o @e a@le to add ne$ati/e /ectors @y scale drain$ ;B +)="

+hat is a 9ector?A /ector is a physical 9uantity that has @oth ma$nitude GsieI and directionB

()amples o 9ectorsD +isplacement. /elocity. force. acceleration and momentumB

+hat is a Scalar?A scalar is a physical 9uantity that has ma$nitude only Git doesnt act in a certaindirectionIB

()amples o ScalarsD +istance. speed. ener$y. poer. pressure.temperature and massB

9ector /iagramsA /ector can @e represented @y a /ector dia$ram as ell as numericallyE&he len$th of the line represents the ma$nitude of the /ectorB&he direction of the line represents the direction of the /ectorB)e can see that /ector ahas a $reater ma$nitude than /ector %@ut acts

in a di-erent directionBA ne$ati/e /ector means a /ector of e9ual ma$nitude @ut oppositedirectionB

Adding 9ectors)e can add /ectors to$ether to nd the a-ect that to or more ould ha/e if actin$ atthe same timeB &his is called the resultant /ectorB )e can nd the resultant /ector in fouraysE Scale drain$. Pytha$oras. the Sine andCosine rules and esol/in$ /ectors Gne#t lessonIB

Scale /rawing&o nd the resultant /ector of

a

%e dra

/ector athen dra /ector %from the end of aB&he resultant is the line that connects the startand nish pointsB

&he resultants of a %, % Xa, a X%, Xa X%andould look like thisE

'f the /ectors ere dran to scale e can ndthe resultant @y measurin$ the len$th of the lineand the an$leB

Pythagoras'f to /ectors are perpendicular to each other theresultant can @e found usin$ Pytha$orasE

0ector Dis the resultant of /ectors 4and yB

Since 4and yare perpendicular 222 yx- += 22 yx- +=

)e can also use this in re/erse to nd 4or yE222 yx- += 222 xy- = xy- = 22222 yx- += 222 yx- = yx- = 22

Sine and Cosine Rules

&he sine rule relates the an$les and len$ths usin$ thise9uationE

c

C

.

/

%

A sinsinsin ==

&he Cosine rule relates them usin$ these e9uationsE

A.cc.% cos2222 +=


27/93

/%cc%. cos2222 +=

C%..%c cos2222 +=?nit 2

esol/in$ 0ectorsLesson 2Learnin$

utcomes

&o @e a@le to resol/e /ectors into their /ertical and horiontal components

&o @e a@le to add /ectors and nd the resultant @y resol/in$ them

&o kno hat e9uili@rium is and ho it is achie/ed ;B +)="

'n the last lesson e looked at ho e could add /ectors to$ether and nd the resultantB'n this lesson e ill rst look at O@reakin$ don the /ectors and then ndin$ thee9uili@riumB

Resol'ing 9ectorsA /ector can @e O@roken don or resolvedinto its /ertical and horiontal componentsB

)e can see that this /ector can @e resol/edinto to perpendicular components. in thiscase to to the ri$ht and three upB

&his is o@/ious hen it is dran on $raphpaper @ut @ecomes trickier hen there isnta $rid and still re9uires an element of scaledrain$B

)e can calculate the /ertical and horiontal components if e kno the ma$nitude anddirection of the /ectorB 'n other ords e can ork out the across and upards @its of the/ector if e kno the len$th of the line and the an$le @eteen it and the horiontal or/ertical a#isB

Adding Resol'ed 9ectors;o that e can resol/e /ectors into the /ertical and horiontal components it is madefrom e can add them to$etherB Look at this e#ample of multiple /ectors actin$ G'IB

' # C > E'f e resol/e the /ector ce $et G#IB )e can no nd the resultant of the horiontalcomponents and the resultant of the /ertical components GCIB )e can then add theseto$ether to nd the resultant /ector G>I and the an$le can @e found usin$ tri$onometry GEI

(7uili*rium)hen all the forces actin$ on a @ody cancel out e9uili@rium isreached and the o@:ect does not mo/eB As you sit and read thisthe donards forces actin$ on you are e9ually @alanced @ythe upards forces. the resultant it that you do not mo/eB


28/93

)ith scale drain$ e can dra the /ectors. one after the otherB 'f e end up in the sameposition e started at then e9uili@rium is achie/edB)ith resol/in$ /ectors e can resol/e all /ectors into their /ertical and horiontalcomponentsB 'f the components up and don are e9ual and the components left and ri$htare e9ual e9uili@rium has @een reachedB

?nit 2

7omentsLesson 3

Learnin$utcomes

&o @e a@le to calculate the moment of a sin$le and a pair of forces

&o @e a@le to e#plain hat the centre of mass and $ra/ity are&o @e a@le to e#plain ho somethin$ @alances and @ecomes sta@le ;B +)="

Moments (Also seen in GCSE Physics 3)&he moment of a force is its turnin$ a-ect a@out a #ed pointGpi/otIB

&he ma$nitude of the moment is $i/en @yEmoment J force # perpendicular distance from force to the pi/ot

0&m"ment=

'n this dia$ram e can see that the force is not actin$

perpendicularly to the pi/otB )e must nd the perpendicular orclosest distance. this is &cos1.

&he moment in this case is $i/en asE cos0&m"ment=

)e could ha/e also used the /alue of &@ut multiplied it @y the/ertical component of the forceB &his ould $i/e us the samee9uationB &0m"ment .cos=

Moments are measured in $e


29/93

'f the seesa to the left is @alanced then the clockise moments must @e e9ual to theanticlockise momentsB

Clockise moment due to 3 and 4

4433 &0&0m"ment +=Anticlockise moments due to 1 and 2

2211 &0&0m"ment +=So 22114433 &0&0&0&0 +=+

Sta*ility (Also seen in GCSE Physics 3)

&he sta@ility of an o@:ect can @e increased @y loerin$ the centre of mass and @yidenin$ the @aseBAn o@:ect ill topple o/er if the line of action of the ei$ht falls outside of the @aseB

?nit 2

0elocity and AccelerationLesson 4Learnin$

utcomes

&o @e a@le to calculate distance and displacement and e#plain hat they are

&o @e a@le to calculate speed and /elocity and e#plain hat they are

&o @e a@le to calculate acceleration and e#plain uniform and nonuniform cases

;B +)="

/istance (Also seen in Physics 2)+istance is a scalar 9uantityB 't is ameasure of the total len$th you ha/emo/edB

/isplacement (Also seen inPhysics 2)

+isplacement is a /ector 9uantityB 't is ameasure of ho far you are from thestartin$ positionB

'f you complete a lap of an athletics trackE distance tra/elled J 4,,mdisplacement J ,

>istance and >is*lacement are measured in metres, m

Speed (Also seen in Physics 2)Speed is a measure of ho the distancechan$es ith timeB Since it isdependent on speed it too is a scalarB

t

d&peed

=

9elocity (Also seen in Physics 2)0elocity is measure of ho thedisplacement chan$es ith timeB Sinceit depends on displacement it is a/ector tooB

t&v=

&*eed and ?elocity are is measured in metres *er second, m"sime is measured in seconds, s

Acceleration (Also seen in Physics 2)Acceleration is the rate at hich the /elocity chan$esB Since /elocity is a /ector 9uantity.so is accelerationB)ith all /ectors. the direction is importantB 'n 9uestions e decide hich direction ispositi/e GeB$B /eI

'f a mo/in$ o@:ect has a positi/e /elocityE j a positi/e acceleration means an increase inthe /elocity

j a ne$ati/e acceleration means a decrease in the/elocityGit @e$ins the Ospeed up in the other directionI

'f a mo/in$ o@:ect has a ne$ati/e /elocityE j a positi/e acceleration means anincrease in the /elocity

Git @e$ins the Ospeed up in the other directionI


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j a ne$ati/e acceleration means a increase in the/elocity

'f an o@:ect accelerates from a /elocity of uto a /elocity of v. and it takes tseconds to do it

then e can rite the e9uations ast

uv%

)( = it may also look like thist

v%

= here

means the Ochan$e in

'cceleration is measured in metres *er second sBuared, m"s2

niorm Acceleration

'n this situation the acceleration is constant X the /elocity chan$es @y the same amounteach unit of timeB!or e#ampleE 'f acceleration is 2ms2. this means the /elocity increases @y 2ms e/erysecondB

&ime GsI , 1 2 3 4 5 %0elocity GmsI , 2 4 ( 1, 12 14

AccelerationGms2I

2 2 2 2 2 2 2

Non-niorm Acceleration'n this situation the acceleration is chan$in$ X the /elocity chan$es @y a di-erent amounteach unit of timeB!or e#ampleE

&ime GsI , 1 2 3 4 5 %0elocity GmsI , 2 1, 1( 2( 3, 44

AccelerationGms2I

2 4 ( 1, 12 14

?nit 2

7otion 6raphsLesson 5Learnin$

utcomes

&o @e a@le to interpret displacementtime and /elocitytime $raphs

&o @e a@le to represent motion ith displacementtime and /elocitytime $raphs

&o kno the si$nicance of the $radient of a line and the area underit ;B +)="


31/93

,radient)e calculate the $radient @y choosin$ to points on the line and calculatin$ the chan$e inthe y a#is GupdonI and the chan$e in the # a#is GacrossIB

Area nder ,raphAt this le/el e ill not @e asked to calculate the area under cur/es. only strai$ht linesB)e do this @e @reakin$ the area into rectan$les G@ase # hei$htI and trian$les G @ase #hei$htIB

/isplacement-Time ,raphs (Also seen in GCSE Physics 2)

A % C

6raph A shos that the displacement stays at 3m. it is stationaryB6raph < shos that the displacement increases @y the same amount each second. it istra/ellin$ ith constant /elocityB6raph C shos that the displacement co/ered each second increases each second. it isacceleratin$B

Sincexy!%dient = andyJ displacement and xJ time t&!%dient =

vel"city!%dient=

9elocity- Time ,raphs (Also seen in GCSE Physics 2)

A % C

6raph A shos that the /elocity stays at 4ms. it is mo/in$ ith constant /elocityB6raph < shos that the /elocity increases @y the same amount each second. it isacceleratin$ @y the same amount each second Guniform accelerationIB

6raph C shos that the /elocity increases @y a lar$er amount each second. theacceleration is increasin$ Gnonuniform accelerationIB

Sincex

y!%dient

= and y J /elocity and # J time

t

v!%dient

=

"n%ccele%ti!%dient=

area J @ase # hei$ht area J time # /elocity %e% ' di&pl%cement

x

y!%dient

=


32/93

&his $raph sho the /elocity decreasin$ in onedirection and increasin$ in the opposite directionB'f e decide that is ne$ati/e and is positi/e then

the $raph tells usE&he o@:ect is initially tra/els at 5 ms

't slos don @y 1ms e/ery secondAfter 5 seconds the o@:ect has stopped't then @e$ins to mo/e

't $ains 1ms e/ery second until it is tra/ellin$ at 5ms

?nit 2

"9uations of 7otionLesson Learnin$

utcomes

&o @e a@le to use the four e9uations of motion

&o kno the correct units to @e used

&o @e a@le to nd the missin$ /aria@leE. s u / a or t ;B +)="

/efning Sym*ols


33/93


34/93

ProFectilesAn o@:ect kicked or thron into the air illfollo a para@olic path like that shon tothe ri$htB'f the o@:ect had an initial /elocity of u.this can @e resol/ed into its horiontal and/ertical /elocity Gas e ha/e seen inLesson 2I

&he horiontal /elocity ill @e ucosand the /ertical /elocity ill @e usin.)ith these e

can sol/e pro:ectile 9uestions usin$ the e9uations of motion e already knoB

HoriGontal and 9ertical Motion&he dia$ram shos to @alls that are released at the same time. one is released and theother has a horiontal /elocityB )e see that the @all shot from the cannon falls at the samerate at the @all that as releasedB &his is @ecause the horiontal and /ertical componentsof motion are independent of each otherB

HoriontalE &he horiontal /elocity is constant esee that the red @all co/ers the same horiontalGacrossI distance ith each secondB

0erticalE &he /ertical /elocity accelerates at a rateof!G*B(1ms2IB )e can see this more clearly inthe released @all it co/ers more distance eachsecondB

&he horiontal /elocity has no a-ect on the/ertical /elocityB 'f a @all ere red from thecannon at a hi$h horiontal /elocity it ouldtra/el further @ut still take the same time to reach the $roundB

?nit 2

;etons LasLesson (Learnin$

utcomes

&o kno and @e a@le to use ;etons 1stla of motion. here appropriate

&o kno and @e a@le to use ;etons 2ndla of motion. here appropriate

&o kno and @e a@le to use ;etons 3rdla of motion. hereappropriate

;B +)="

Newton>s ;st#awAn o@:ect ill remain at rest. or continue to mo/e ith uniform /elocity. unless it is actedupon @y an e#ternal resultant forceB

Newton>s s =rd#aw

)hen @ody A e#erts a force on @ody


35/93

&he acceleration of an o@:ect increases hen the force is increased @ut decreases hen

the mass is increasedEm

0%= @ut e rearran$e this and use m%0=

Newton>s =rd#aw!orces are created in pairsBAs you sit on the chair your ei$ht pushes don on the chair. the chair also pushes upa$ainst youBAs the chair rests on the >oor its ei$ht pushes don on the >oor. the >oor also pushesup a$ainst the chairB

&he forces ha/e the same sie @ut opposite directionsBRiding the %usNewton>s ;st#aw

=ou $et on a @us and stand upB )hen the @us is stationary you feel no force. hen the @usaccelerates you feel a @ackards forceB =ou ant to stay here you are @ut the @us forcesyou to mo/eB )hen the @us is at a constant speed you feel no forards or @ackardsforcesB &he @us slos don and you feel a forards forceB =ou ant to keep mo/in$ at thesame speed @ut the @us is sloin$ don so you fall forardsB 'f the @us turns left youant to keep mo/in$ in a strai$ht line so you are forced to the ri$ht Gin comparison to the@usIB 'f the @us turns ri$ht you ant to keep mo/in$ in a strai$ht line so you are forced leftGin comparison to the @usIB

Newton>s s =rd#awAs you stand on the @us you are pushin$ don on the >oor ith a force that is e9ual toyour ei$htB 'f this as the only force actin$ you ould @e$in to mo/e throu$h the >oorB

&he >oor is e#ertin$ a force of e9ual ma$nitude @ut upards Gin the opposite directionIB

Ta"ing the #itNewton>s ;st#aw

)hen you $et in the lift and hen it mo/es at a constant speed you feel no force up ordonB )hen it sets o- $oin$ up you feel like you are pushed don. you ant to stayhere you areB )hen it sets o- $oin$ don you feel like you are li$hter. you feel pulled

upBNewton>s s =rd#awAs you stand in the lift you push don on the >oor. the >oor pushes @ackB

?nit 2

)ork. "ner$y and PoerLesson *

Learnin$utcomes

&o @e a@le to calculate ork done Gincludin$ situations in/ol/in$ an inclined

planeI&o @e a@le to calculate the poer of a de/ice

&o @e a@le to calculate eciency and percenta$e eciency ;B +)="

(nergy (Also seen in GCSE Physics 1))e already kno that it appears in a num@er of di-erent forms and may @e transformedfrom one form to anotherB


36/93

&he distance mo/ed is not alays in the direction of the forceB 'n the dia$ram e can see

that the @lock mo/es in a direction that is aay from the Oline of action of the forceB &o

calculate the ork done e must calculate the distance e mo/e in the direction of theforce or the sie of the force in the direction of the distancemo/edB


37/93

(nergy Transormations (Also seen in GCSE Physics 1))e already kno that ener$y cannot @e created or destroyed. only transformed from onetype to another and transferred from one thin$ to anotherB "$ a speaker transformselectrical ener$y to sound ener$y ith the ener$y itself is @ein$ transferred to thesurroundin$sBAn isolated Gor closedI system means an ener$y transformation is occurrin$ here noneof the ener$y is lost to the surroundin$sB 'n reality all transformationstransfers are notisolated. and all of them aste ener$y to the surroundin$sB

inetic (nergy (Also seen in GCSE Physics 2)8inetic ener$y is the ener$y a mo/in$ o@:ect hasB Let us consider a car that acceleratesfrom @ein$ stationary GuJ,I to tra/ellin$ at a /elocity vhen a force. 0. is appliedB

&he time it takes to reach this /elocity is $i/e @y %tuv += %tv = %

vt=

&he distance mo/ed in this time is $i/en @y tvu& )(21

+= tv& )(21=

%

vv& )(

21=

%

v&

2

21=

"ner$y transferred J )ork +one. )ork +one J !orce # distance mo/ed and !orce J mass# acceleration

4E= 0&E= m%&E= %

vm%E

2

21= 22

1 mvEK=

?elocity is measured in metres *er second, m"sMass is measured in kilograms, kg

/inetic Energy is measured in :oules, :

,ra'itational Potential (nergy&his type of potential GstoredI ener$y is due to the position of an o@:ectB 'f an o@:ect ofmass m is lifted at a constant speed @y a hei$ht of he can say that the acceleration iseroB Since 69mae can also say that the o/erall force is ero. this means that the liftin$force is e9ual to the ei$ht of the o@:ect 0'm!

)e can no calculate the ork done in liftin$ the o@:ect throu$h a hei$ht. hB

0&45= hm!45 )(= m!h45=Since ork done J ener$y transferred hm!EP =

eight is a measure o= distance


38/93

Learnin$utcomes

&o @e a@le to state Hookes La and e#plain hat the sprin$ constant is

&o @e a@le to descri@e ho sprin$s @eha/e in series and parallel

&o @e a@le to deri/e the ener$y stored in a stretched material ;B +)="

Hoo"e>s #aw'f e take a metal ire or a sprin$ and han$ it from the ceilin$ it ill ha/e a natural.unstretched len$th of lmetresB 'f e then attach masses to the @ottom of the ire is ill@e$in to increase in len$th GstretchIB &he amount of len$th it has increased @y e ill call

the e#tension and represent @y eB'f the e#tension increases proportionally to the force applied it follos Hookes LaEhe %orce needed to stretch a spring is directly proportional to the e,tension o% the spring

%rom its natural lengthSo it takes tice as much force to e#tend a sprin$ tice as far and half the force to e#tendit half as farB)e can rite this in e9uation formE e0 or 3e0=Here 3is the constant that shos us ho much e#tension in len$th e ould $et for a$i/en forceB 't is calledBBB

The Spring Constant&he sprin$ constant $i/es us an idea of the sti-ness Gor stretchinessIof the materialB

'f e rearran$e Hookes La e $etEe

03=

'f e record the len$th of a sprin$. add masses to the @ottom andmeasure its e#tension e can plot a $raph of force a$ainst e#tensionB

&he $radient of this $raph ill @e e9ual to the sprin$ constantBA small force causes a lar$e e#tension the sprin$ constant ill @esmallX very stretchyA lar$e force causes a small e#tension the sprin$ constant ill @e largeX not stretchy

&*ring Constant is measured in $e


39/93

&he force is not constant it increases from ero to a ma#imum of0B &he a/era$e force is

$i/en @yE2

)0( 0

'f e @rin$ these terms to$ether e $et the e9uation e0

E2

)0( = hich simplies toE

0eE21=

his is also e&ual to the area under the graph o% %orce against e,tension$)e can rite a second /ersion of this e9uation @y su@stitutin$ our top e9uation of 3e0=

into the one a@o/eB0eE

21

= e3eE )(21= 221 3eE=

?nit 2

Stress and StrainLesson 12Learnin$

utcomes

&o kno hat stress is. @e a@le to e#plain it. calculate it and state its units

&o kno hat strain is. @e a@le to e#plain it. calculate it and state its units

&o @e a@le to calculate the elastic strain ener$y per unit /olume ;B +)="

/eorming Solids

!orces can @e used to chan$e the speed. direction and shape of an o@:ectB &his section ofPhysics looks at usin$ forces to chan$e of shape of a solid o@:ect. either temporarily orpermanentlyB'f a pair of forces are used to s&uasha material e say that they are compressiveforcesB

'f a pair of forces is used to stretcha material e say that they are tensileforcesB

Tensile Stress6 &ensile stress is dened as the force applied per unit crosssectional area Ghich is thesame as pressureIB

&his is represented @y the e9uationsE

A

0&te&&=

A

0=

&he lar$est tensile stress that can @e applied to a material @efore it @reaks is called theultimate tensile stress G?&SIB ;ylon has an ?&S of (5 7Pa hilst Stainless steel has a/alue of ,, 7Pa and 8e/lar a massi/e 31,, 7Pa

&tress is measured in $e


40/93

(lastic Strain (nergy)e can @uild on the idea of ener$y stored from the pre/ious lesson no that e knohat stress and strain areB )e can ork out the amount of elastic strain ener$y that isstoredper unit volumeof the materialB

't is $i/en @y the e9uationE &t%in&te&&E = 21

&here are to routes e can take to arri/e at this resultE(7uations

'f e start ith the e9uation for the total ener$y stored in the materialE 0eE 21

=

&he /olume of the material is $i/en @yE AlV=;o di/ide the total ener$y stored @y the /olumeE

Al

0eE 2

1

= hich can @e ritten asE

l

e

A

0E

21=

'f e compare the e9uation to the e9uations e kno for stress and strain e see thatE

&t%in&te&&E =21

,raphs&he area under a stressstrain $raph $i/es us the elastic strain ener$y per unit /olumeGm3IB &he area is $i/en @yE

hei!ht.%&eA = 21 &te&&&t%inA = 21 or &t%in&te&&A = 21

&t%in&te&&E =21

?nit 2


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42/93

Sincex

y!%dient

= . this @ecomes

&t%in

&te&&!%dient= for our $raphB ur top e9uation stated

that&t%in

&te&&u&Y"un!7"dul = so e see that the $radient of a stressstrain $raph $i/es us

the =oun$ 7odulusB&his only applied to the strai$ht line section of the $raph. here $radient Gand =oun$7odulusI are constantB

Measuring the Joung ModulusHere is a simple e#perimental set up for ndin$ the =oun$ 7odulus of a materialB

A piece of ire is held @y a 6clamp.

sent o/er a pulley ith the smallestmass attached to itB &his shouldkeep it strai$ht ithout e#tendin$ itB

7easure the len$th from the clamp

to the pointerB &his is the ori$inallen$th GunstretchedIB

?se a micrometer to measure the

diameter of the ire in se/eral placesB ?se this to calculate the crosssectional area of

the ireB Add a mass to the loaded end of the ireB

ecord the e#tension @y measurin$ ho far the pointer has

mo/ed from its start positionB

epeat for se/eral masses @ut ensurin$ the elastic limit is not

reachedB

emo/e the masses. one at a time takin$ another set of

readin$ of the e#tensionB

Calculate stress and strain for each massB

Plot a $raph of stress a$ainst strain and calculate the $radient

of the line hich $i/es the =oun$ 7odulusB

Here is a more precise ay of ndin$ the =oun$ 7odulus @utin/ol/es takin$ the same measurements of e#tension and forceappliedB't is called Searles apparatusB

?nit 2

Pro$ressi/e )a/esLesson 15Learnin$

utcomes

&o @e kno the @asic measurements of a a/e

&o @e a@le to calculate the speed of any a/e

&o @e kno hat phase and path di-erence are and @e a@le to

calculate them ;B +)="

+a'esAll a/es are caused @y oscillations and all transfer ener$y ithout transferrin$ matterB

&his means that a ater a/e can transfer ener$y to you sittin$ on the shore ithout theater particles far out to sea mo/in$ to the@eachBHere is a dia$ram of a a/e it is one type ofa/e called a trans/erse a/eB A a/e consistsof somethin$ Gusually particlesI oscillatin$ froman e9uili@rium pointB &he a/e can @e descri@ed

as pro$ressi/e this means it is mo/in$ outards from the sourceB)e ill no look at some @asic measurements and characteristics or a/esB

Amplitude6A 'm*litude is measured inmetres, m

&he amplitude of a a/e is the ma#imum displacement of the particles from thee9uili@rium positionB


43/93

+a'elength6; Wavelength is measured inmetres, m

&he a/elen$th of a a/e is the len$th of one hole cycleB 't can @e measured @eteento ad:acent peaks. trou$hs or any point on a a/e and the same point one a/e laterB

Time Period6 ime Period is measured inseconds, s

&his is simply the time is takes for one complete a/e to happenB Like a/elen$th it can@e measured as the time it takes @eteen to ad:acent peaks. trou$hs or to $et @ack tothe same point on the a/eB

&re7uency6 % 3reBuency is measured inertD, D

!re9uency is a measure of ho often somethin$ happens. in this case ho many completea/es occur in e/ery secondB 't is linked to time period of the a/e @y the folloin$

e9uationsEf

T 1= and

Tf

1=

+a'e Speed6 c Wave &*eed is measured in metres*er second, m s1

&he speed of a a/e can @e calculated usin$ the folloin$ e9uationsE fc=

Here crepresents the speed of the a/e. fthe fre9uency and 8the a/elen$thB

Phase /i$erence Phase >iIerence is measured in

radians, rad'f e look at to particles a a/elen$th apart Gsuch as C and 6I e ould see that theyare oscillatin$ in time ith each otherB )e say that they are completelyin phaseB &opoints half a a/elen$th apart Gsuch as ' and 8I e ould see that they are alaysmo/in$ in opposite directionsB )e say that they are completely out o% phaseB

&he phase di-erence @eteen to points depends on hat fraction of a a/elen$th lies@eteen them

< C + " ! 6 H ' ` 8 L 7Phase +i-erencefrom A GradiansI

Y 1Y 1Y 2Y 2Y 3Y 3Y 4Y 4Y 5Y 5Y Y

Phase +i-erencefrom A Gde$reesI

*, 1(, 2%, 3, 45, 54, 3, %2, (1, *,, **,1,(,

Path /i$erence Path >iIerence is measured in


44/93

+a'esAll a/es are caused @y oscillations and all transfer ener$y ithout transferrin$ matterB

&his means that a sound a/e can transfer ener$y to your eardrum from a far speakerithout the air particles @y the speaker mo/in$ into your earB )e ill no look at the totypes of a/es and ho they are di-erent

#ongitudinal +a'esHere is a lon$itudinal a/e the oscillations are parallel to the direction of propa$ationGtra/elIB

)here the particles are close to$ether e call a compression and here they are spreade call a rarefactionB

&he a/elen$th is the distance from one compression or rarefaction to the ne#tB&he amplitude is the ma#imum distance the particle mo/es from its e9uili@rium positionto the ri$ht of leftB

E,ampleu# density

Geld stren$thI that causes a 1 ;eton force to act on 1 metre of ire carryin$ 1 Amp ofcurrentB

Magnetic 3lu4 >ensity is measured in esla,

&his e9uation looks /ery familiar if e compare it to the force in a $ra/itational andelectric eldB !m0 .= E20 .= /Il0 .=

?nit 4

!orce on a Char$ed ParticleLesson 1*

Learnin$utcomes

&o @e a@le to calculate the sie and direction of the force on a char$ed particle ina ma$netic eld

&o @e a@le to descri@e the motion of a char$ed particle in a ma$netic eld

&o @e a@le to descri@e the main features of a cyclotron and e#plainho it orks

;B +)="

&orce on Charged Particle!rom our e9uation for the force a ma$netic eld ill e#ert on a ire e can deri/e ae9uation for the force it ill e#ert on a sin$le char$ed particleB

Start ith /Il0= B 'n ?nit 1 e dened the current ast

QI= so e can su@ this in to

@ecome lt

Q/0=

)e can rerite this e9uationt

l/Q0= and use

t

lv= from ?nit 2 to arri/e at the e9uationE

/Qv0 =

Mo'ing in a Circle'f a char$ed particle enters a ma$netic eld it ill feel aforceB )e no kno the sie of the force G$i/en @y e9uationa@o/eI and direction of the force G$i/en @y !lemin$s LeftHand uleIB'f e use the left hand rule in the dia$ram to the ri$ht ecan see that the force is alays at ri$ht an$les to the /elocityB !irst n$erpoints into the pa$e. middle n$er points alon$ the line and our thum@points upardsB)hile the particle is in the ma$netic eld it ill mo/e in a circleB

Radius o the circle)e can calculate the radius a char$ed particle ill mo/e in @y usin$ our e9uation for theforce on a char$ed particle in a ma$netic eld and a centripetal force e9uationB


73/93


74/93

&his is hy a ma$net is stron$est at its poles there is a hi$h concentration of eld linesB

)e can see that the amount of >u# >oin$throu$h a loop of ire depends on thean$le it makes ith the eld linesB &heamount of >u# passin$ throu$h the loop is$i/en @yE

cos/A=1is the an$le that the normal to the loop

makes ith the eld linesBMagnetic &lu) /ensity)e can no see hy /is called the ma$netic >u# densityB 'f e rearran$e the tope9uation for/e $etE

A/

= So/is a measure of ho many >u# lines Geld linesI passes throu$h each unit area

Gper m2IBA >u# density of 1 &esla is hen an area of 1 metre s9uared has a >u# of 1 )e@erB

&lu) #in"age)e no kno that the amount of >u# throu$h one loop of ire isE /A='f e ha/e a coil of ire made up of =loops of ire the total >u# is $i/en @yE

/A== =

&he total amount of >u#. = . is called the *agnetic 6lu, #in'age this is @ecause econsider each loop of ire to @e linked ith a certain amount of ma$netic >u#BSometimes >u# linka$e is represented @y . so == hich makes our e9uation for>u# linka$e /A==

3lu4 inkage is measured in We%ers, W%

Rotating Coil in a Magnetic &ield'f e ha/e a rectan$le of ire that has an area of Aand e place it in a ma$netic eld of>u# density /. e ha/e seen that the amount of >u# >oin$ throu$h the ire depends onthe an$le @eteen it and the >u# linesB

&he >u# linka$e at an an$le 1from the perpendicular to the ma$netic eld is $i/en @yE cos/A== =

!rom our lessons on circular motion e esta@lished that the an$ular speed is $i/en @y

t

= hich can @e rearran$ed to t= and su@stituted into the e9uation a@o/e to

transform it intoE t/A== cos=

)hen t J , the ire is perpendicular to the eld so there is a ma#imum amount of >u#B

At 1 the >u# linka$e is a ma#imum in one directionB &here is the loest rate of chan$e atthis pointBAt 2 the >u# linka$e is eroB &here is the @i$$est rate of chan$e at this pointAt 3 the >u# linka$e is ma#imum @ut in the opposite directionB &he loest rate of chan$eoccurs here tooBAt 4 the >u# linka$e is eroB &here is the @i$$est rate of chan$e at the point too @ut in theopposite directionB

;e#t lesson e ill @e lookin$ at inducin$ an eBmBfB usin$ a ire and a ma$netic eldB &hesie of the eBmBfB depends on the rate of chan$e of >u# linka$eB

?nit 4

"lectroma$netic 'nductionLesson 21&o kno ho emf and current are induced

&o kno !aradays La and @e a@le to use it to descri@e the induced emf


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'f e are :ust mo/in$ a strai$ht ire throu$h a uniform ma$netic eld the direction of theinduced current can @e orked out usin$ !lemin$s i$ht Hand uleB

=our rst n$er points in the direction of the eld from ;orth to South. your thum@ pointsin the direction the ire is mo/ed and your middle n$er points in the direction of thecon/entional currentB

?nit 4

&ransformersLesson 22

Learnin$utcomes

&o @e a@le to descri@e a transformer and calculate the /olta$e and current in the

secondary coil&o @e a@le to calculate the eciency of a transformer and e#plain hy they areused

&o @e a@le to state the causes of ineciency in transformers ;B +)="

Transormers (Also seen at GCSE Physics 3)A transformer is a de/ice used to chan$e the /olta$ecurrentof a circuit usin$ electroma$netic inductionB 't consists of asoft iron core rapped on @oth side ith ireB &he rst coil ofire is called the primary coil and the other coil of ire iscalled the secondary coilB

A current doesnt >o from one coil of ire to the otherBHow They +or"

A current >os throu$h the primary coil hich creates ama$netic eldBAs this eld is esta@lished the eld lines cut throu$h the turns of ire on the secondarycoilB &his induces an eBmBfB G/olta$eI and a current in the second coilBSince the supply to the primary coil is constantly chan$in$ direction the ma$netic eld isconstantly chan$in$ directionB &his means the secondary coil also has an alternatin$eBmBfB and currentBAn iron core is used @ecause it is easily ma$netised and dema$netised and conducts thema$netic eldB

Transorming 9oltage and Current (Also seen at GCSE Physics 3)&here are to types of transformersEStep p

&he /olta$e in the secondary coil is lar$er than the /olta$e in the primary coilB&he current in the secondary coil is smaller than the current in the primary coilB

here +ill be more turns o% +ire on the secondary coil meaning more 0u, lin'ageStep /own

&he /olta$e in the secondary coil is smaller than the /olta$e in the primary coilB&he current in the secondary coil is lar$er that the current in the primary coilB

here +ill be %e+er turns o% +ire on the secondary coil meaning less 0u, lin'age

'n @oth cases the /olta$e and current GVPandIPI in the primary coil of =Pturns is linked tothe /olta$e and current GV?andI?I in the secondary coil of =?turns @y the folloin$e9uationE

?

P

P

?

P

?

I

I

V

V

=

===

The National ,rid (Also seen at GCSE Physics 1)&he ;ational 6rid is a system of transformers that increases the /olta$e Greducin$ thecurrentI of an alternatin$ electrical supply as it lea/es the poer stationB &hick ca@les helda@o/e the $round @y pylons carry the supply to our nei$h@ourhoodB A second series oftransformers loers the /olta$e to a safe le/el and increases the current to @e used in ourhomesB

+hy %other?"ner$y is lost in the transmission of electricityB &he electrons >oin$ in the ire areconstantly collidin$ ith the positi/e ions of the metal that the ire is made fromB 'f eincrease the /olta$e of a supply this loers the currentB Loerin$ the current reduces the


77/93

num@er of collisions happenin$ per second hence reducin$ the amount of ener$y lost inreachin$ our homesB

&he ca@les that carry the current ha/e a lar$er cross sectional area. this loers theresistance and ener$y lostB

(ciency o a Transormer&he eciency of a transformer can @e calculated usin$ the folloin$ e9uationE

"ciencyPP

??

VI

VI=

&he eciency of a transformer can @e increased @yEj?sin$ lo resistance indin$s to reduce the poer asted due to the heatin$ e-ect ofthe currentBj?se a laminated core hich consists of layers of iron separated @y layers of insulationB&his reduces heatin$ in the iron core and currents @ein$ induced in the core itselfGreferred to as eddy currentsIB

?nit 5

utherford Scatterin$Lesson 1Learnin$

utcomes

&o kno the set up of utherfords e#periment and the results he found

&o @e a@le to e#plain ho the results are e/idence for the nucleus

&o kno the factors e must consider hen choosin$ the particle eill scatter

;B +)="

Rutherord>s Scattering ()periment (Also seen in GCSEPhysics 2)

Hans 6ei$er and "rnest 7arsdenorked ith "rnest utherford inhis 7anchester la@oratories in1*,*B &hey red alpha particlesGhich they kne to ha/e apositi/e char$eI of a fe 7e0 intoa thin piece of $old foilB &his asdone in an e/acuated cham@erconnected to a /acuum pumpB)hen the alpha particles passed

throu$h the $old foil they hit a inc sulphide screen hich emitsli$ht hene/er an alpha particle strikes itB &his screen aso@ser/ed usin$ a mo/in$ microscope in a dark roomBAt the time the accepted structure of the atom as like a plumpuddin$E positi/e dou$h spread e/enly ith ne$ati/e electronsscattered throu$h out it like plums in a puddin$B

Results (Also seen in GCSE Physics 2)6ei$er and 7arsden found that almost all of the alpha particlespassed throu$h ith little or no de>ectionB utherford su$$estedmo/in$ the microscope in front of the foil. hen they did theyfound that a@out 1 in e/ery (,,, as Ore>ected @ack or scatteredthrou$h an an$le of more that *,B'f the plum puddin$ model as the structure of the atom this ould@e like rin$ a @ullet at a piece of toilet paper and it @ouncin$ @ackX mental

The Nuclear Model (Also seen in GCSE Physics 2)

utherford used these results to make the folloin$ conclusionsE7ost of the mass must @e $athered in one small /olume X thenucleusB

hey can repel a %ast moving alpha particle

&he nucleus must @e positi/ely char$edBhey repel positive alpha particles

7ost of the atom is empty spaceB
http://images.google.co.uk/imgres?imgurl=http://physics.uwstout.edu/geo/bedtime/graphics/atom.jpg&imgrefurl=http://physics.uwstout.edu/geo/bedtime/daddy%27s%2520stories.htm&usg=__iC3F2RTHiCYC0NWQFQdryW00_p0=&h=650&w=723&sz=40&hl=en&start=10&um=1&tbnid=mnVIyfIA21j65M:&tbnh=126&tbnw=140&prev=/images%3Fq%3Datom%26um%3D1%26hl%3Den%26rlz%3D1T4HPEA_enGB309GB309http://images.google.co.uk/imgres?imgurl=http://physics.uwstout.edu/geo/bedtime/graphics/atom.jpg&imgrefurl=http://physics.uwstout.edu/geo/bedtime/daddy%27s%2520stories.htm&usg=__iC3F2RTHiCYC0NWQFQdryW00_p0=&h=650&w=723&sz=40&hl=en&start=10&um=1&tbnid=mnVIyfIA21j65M:&tbnh=126&tbnw=140&prev=/images%3Fq%3Datom%26um%3D1%26hl%3Den%26rlz%3D1T4HPEA_enGB309GB309http://images.google.co.uk/imgres?imgurl=http://physics.uwstout.edu/geo/bedtime/graphics/atom.jpg&imgrefurl=http://physics.uwstout.edu/geo/bedtime/daddy%27s%2520stories.htm&usg=__iC3F2RTHiCYC0NWQFQdryW00_p0=&h=650&w=723&sz=40&hl=en&start=10&um=1&tbnid=mnVIyfIA21j65M:&tbnh=126&tbnw=140&prev=/images%3Fq%3Datom%26um%3D1%26hl%3Den%26rlz%3D1T4HPEA_enGB309GB309


78/93

7nly 1 in FFF alpha particles are de0ected;e$ati/e electrons or@it the nucleus at a lar$e distance from itB

"egative charges are needed to 'eep the atom neutral

+hich Particle to se?&here are to thin$s to consider hen usin$ scatterin$ to nd the structure of thin$sE theparticle and the ener$y

Alpha ScatteringE utherford used alpha particles ith ener$ies around 47e0. anyhi$her and it ould @e close enou$h to the nucleus to e#perience the stron$ nuclear forceB

(lectron ScatteringE "lectrons are accelerated to hi$h ener$ies of around 6e0B &heyha/e enou$h ener$y to @e scattered ithin protons and neutrons disco/erin$ 9uarksB"lectrons tra/ellin$ at this speed ha/e a de


79/93

The In'erse-S7uare #aw6amma radiation from a source ill spread outB &he radiation from a small source can @econsidered the same in all directions GisotropicI. ima$ine a sphere around the sourceB Ase mo/e further aay from the source the @i$$er the sphere $etsB &he same amount ofener$y is shared o/er a $reater surface areaB &he further e mo/e from the source theless intensity of the $amma radiationB

ntensity is measured in Watts, W&he intensity.I. of the radiation at a distance xfrom the source is $i/en as

)hereI0is the intensity at the source and 3is a constantB

)e do not alays need to kno the intensity at the source to nd it at a $i/en distanceBConsider to points. A and uence it at all GeB$B pressure andtemperatureIB)hat e can do is $i/e a pro@a@ility that a nucleus ill decay in a $i/en timeB

/ecay Constant6"/ery radioacti/e isotope has its on pro@a@ility that a nucleus ill decay. called thedecay constantB

Acti'ity6 A

&he acti/ity of a radioacti/e source is the num@er of decays that happen e/ery secondB1 @ec9uerel is e9ual to one decay per second. 5, @ec9uerels is e9ual to 5, decay persecond.

'ctivity is measured in %ecBuerels, #B (decays *er second, s1)+urin$ a certain amount of time. t. some radioacti/e atoms G=)decay from a sample of"atomsB

2

0

x

3II =


80/93

&he chan$e in the num@er of nuclei in a certain time is =t

==

this can @e ritten as

=A =&he minus si$n is there @ecause e are losin$ nuclei. the num@er e ha/e left is $ettin$smallerB

()ponential /ecayAs time passes the num@er of nuclei that decay e/ery second illdecreaseB

&o calculate the num@er of nuclei that e ha/e left after a time. t. is $i/en @yE)here=0is the num@er of nuclei at the start and =is the current num@er of nucleiB &his issimilar to the e#ponential decay e9uation of a dischar$in$ capacitorB

&he e9uation for calculatin$ the acti/ity looks similarE

Hal-#ie (Also seen in GCSE Physics 1)"ach radioacti/e isotopes has its on halflifeB )e already kno that it isEhe time it ta'es %or the number o% atoms in a sample to drop to hal% o% its original sampleorhe time it ta'es %or the activity o% a substance to drop to hal% o% its original activity

al=i=e is measured in seconds, s

&he half life of a su@stance is linked to the decay constantB'f there is a hi$h pro@a@ility that a nucleus ill decay GJ


81/93

+hy doesn>t it ollow NQ?Protons repel each other ith the electroma$netic force @ut the stron$ nuclear force isstron$er at small distances and keeps them to$ether in the nucleusB )e can see the lineof sta@ility follos ;JF at lo /aluesBAs the nucleus $ets @i$$er there are more protons. hen they @ecome a certain distanceapart they no lon$er e#perience the stron$ nuclear force that keeps them to$ether. onlythe electroma$netic hich pushes them apartB &o keep the nucleus to$ether e needmore neutrons hich feel no electroma$netic repulsion only the attraction of the stron$nuclear forceB

Points to remem*er!ollos ;JF around FJ2,. then cur/es to $o throu$h FJ(, ;J12,emitters a@o/e the line. emitters @elo the line and at the top

Alpha /ecay (Also seen in GCSE Physics 2)An alpha particle Ga Helium nucleusI is e:ected from the parent nucleusB

424

2 + YX

A

Z

A

Z ossO2 protons. 2 neutrons

%eta Minus /ecay (Also seen in GCSE Physics 2)A neutron is transformed into a proton Gthat stays in the nucleusI and an electron Ghichis emittedIB

eA

Z

A

Z eYX ++ +0

11ossO1 neutron GainO1 proton

%eta Plus /ecayA proton is transformed into a neutron and a positronB

e

A

Z

A

Z eYX ++ +0

11 ossO1 proton GainO1 neutron

(lectron CaptureA nucleus can capture one of the or@itin$ electronsB A proton chan$es into a neutronB

e

A

Z

A

Z YeX ++ 10

1 ossO1 proton GainO1 neutron

Nucleon (mission /ecay't is possi@le for an unsta@le isotope to emit a nucleonfrom the nucleusB'n protonrich or protonhea/y nuclei it is possi@le Gthou$hrareI for a proton to @e emittedB

pYX AZA

Z

1

1

1

1 + ossO1 proton

'n neutronrich or neutronhea/y nuclei it is possi@leGthou$h rareI for a neutron to @e emittedB

nXX AZA

Z

1

0

1 + ossO1 neutron

,amma Ray (mission (Also seen in GCSE Physics 2)Alpha emission is often folloed @y $amma ray emissionB

&he dau$hter nuclei are left in an e#cited stateGremem@er ener$y le/els from ?nit 1I hich they ill atsome point fall from to the $round state. emittin$ a

$amma photonB &here is no nuclear structure chan$e.:ust a chan$e of ener$yB

+ XX AZA

ZossO"ner$y

?nit 5

;uclear adiusLesson 5

Learnin$utcomes

&o @e a@le to calculate the radius of a nucleus @y the closest approach of alphaparticles

&o @e a@le to calculate the radius of a nucleus @y the di-raction an$le ofelectrons

&o @e a@le to calculate the nuclear radius and nuclear density ;B +)="

utherford $a/e us an idea of the sie of the nucleus compared to the atom @ut moree#perimental ork has @een done to nd a more accurate measurementB


82/93

Closest Approach o AlphaParticles

utherford red alpha particles at $old atomsin a piece of foilB &hey approach the nucleus@ut slo don as the electroma$neticrepulsi/e force @ecome stron$erB "/entuallythey stop mo/in$. all the kinetic ener$y has @een con/erted into potential ener$y as theparticles come to rest at a distance from the centre of the nucleusB

PK EE = 2VEP= here Vis the electric potential at a distance of from the centre

Q2EP

04=

Q2EK

04=

KE

Q2

04

=

&his $i/es us the upper limit of the radius of a nucleusBCalculatin$ the nuclear radius this ay $i/es us a /alue of J 4B55 # 1,14m or 45B5 fmGhere 1 fm J 1 # 1,15mI7odern measurements $i/e us /alues of appro#imately J B5 fm

Gemem@er that 1 e0 of ener$y is e9ual to 1B # 1,1*`I

(lectron /i$ractionA @eam of electrons ere red at a thin sample ofatoms and the di-raction pattern as detected and

then e#aminedB

&he $raph shos aminimum at a /alue of1minB )e can use this tond a /alue of thenuclear radiusB

5

61.0sin min=

)here5is the nuclear radius and 8is the de


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V

m= 334 R

Au

=

3

034 )( 3

1

A

Au

=

A

Au3

034

=

3

034

u

=

)e can see that the density is independent of the nucleon num@er and $i/es a /alue ofE3B4 # 1,1%k$ m3B

?nit 5

7ass and "ner$yLesson Learnin$

utcomes

&o @e a@le to e#plain hat mass defect is and @e a@le to calculate

&o @e a@le to e#plain hat @indin$ ener$y is and @e a@le to calculate

&o @e a@le to sketch the $raph of


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)e can no calculate the @indin$ ener$y of the Helium nucleus to @eE EJ 2% 7e0G2% million e0I

%inding (nergy ,raph&he @indin$ ener$y is the ener$y re9uiredto separate a nucleus into its constituentnucleonsB &he @indin$ ener$y per nucleon$i/es us the ener$y re9uired to remo/e oneproton or neutron from the nucleusB

&he $raph of @indin$ ener$y per nucleona$ainst nucleon num@er looks like thisB

&here is an increase in the ener$y re9uiredto remo/e one nucleon up until the peak of(B( 7e0 at 'ron 5B &he line then $entlydecreasesB &his means 'ron is the moststa@le nucleus @ecause it re9uires thelar$est amount of ener$y to remo/e onenucleonB &his ill also mean that there isthe $reatest mass defectB

?nit 5

!ission and !usionLesson %Learnin$

utcomes

&o kno hat occurs in nuclear ssion and nuclear fusion processes

&o kno hat a chain reaction is. ho it occurs and hat critical mass is

&o @e a@le to state and e#plain hether ssion or fusion ill occur ;B +)="

Nuclear &ission (Also see GCSE Physics 2)6ission occurs +hen a nucleus splits into t+o smaller nuclei

)e make ssion happen @y rin$ slo mo/in$ neutrons at ?ranium 235. Plutonium 23* or&horium 232 nucleiB )e call this induced 4ssionB 'n this processes the nucleus a@sor@s aneutron then splits to form to li$hter nuclei. releases ener$y and any neutrons left o/er.

usually 2 or 3BHere is a possi@le e9uation for the ssion of ?ranium 235E

E%&edene!yelenK/%n 2 1090

36

144

56

1

0

235

92 ++++

Chain Reaction'n the a@o/e reaction to free neutrons erereleased. these can also @e a@sor@ed @y tohea/y nuclei and cause a ssion processB

&hese nuclei ould release more neutronshich could cause further ssions and so onB

Critical Mass!or a chain reaction to happen the mass of thessiona@le material must @e $reater than acertain minimum /alueB &his minimum /alue isknon as the critical massand is hen thesurface area to mass ratio is too smallB

'f mass g critical massE more neutrons are escapin$ than are producedB Stops'f mass J critical massE num@er of neutrons escapin$ J num@er of neutrons producedBSteady'f mass critical massE more neutrons are produced than are escapin$B 7eltdon

Nuclear &usion(Also see GCSE Physics 2)6usion occurs +hen t+o nuclei Boin to %orm a bigger nucleus

&he to nuclei must ha/e /ery hi$h ener$ies to @e mo/in$ fast enou$h to o/ercome theelectrostatic repulsion of the protons then. hen close enou$h. the stron$ nuclear forceill pull the to nuclei to$etherBHere is an e#ample of the fusin$ of to hydro$en isotopesE

E%&edene!yelenHeHH 104

2

3

1

2

1 +++


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+hich +ill Happen?Lookin$ at the $raph e can see the 'ron 5 hasthe hi$hest @indin$ ener$y per nucleon. themost ener$y re9uired to remo/e one proton orneutron from the nucleusB &his makes it the moststa@leB

"uclei lighter than Iron +ill undergo %usion$Protons and neutrons feel the attraction of the

stron$ nuclear force @ut only protons feel therepulsion of the electrostatic forceB !or li$htnuclei. addin$ an e#tra proton increases thestron$ nuclear force to pull the nucleon to$etherB

&his is @ecause at this ran$e the sBnBfB force isstron$er than the other three fundamental forcesB

&he nucleons mo/e closer to$ether potential ener$y is lost ener$y is $i/en out

"uclei heavier than Iron +ill undergo 4ssion$


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more easilyB &he ?ranium that is used in fuel rods has a hi$her percenta$e of 235 and issaid to @e enrichedB &his is so more ssion reactions may take placeB

Moderator!oleO&he neutrons that are $i/en out from nuclear ssion are tra/ellin$ too fast to causeanother ssion processB &hey are released at 1 # 1,%ms and must @e sloed to 2 # 1,3ms. losin$ **B***%5N of their kinetic ener$yB &he neutrons collide ith the atoms of themoderator hich turns the kinetic ener$y into heatB;eutrons that are tra/ellin$ slo enou$h to cause a ssion process are called thermalneutrons. this is @ecause they ha/e the same amount of kinetic ener$y as the atoms of

the moderator Ga@out ,B,25 e0 at 2,CIB3actors aIecting the choice o= materialsO7ust ha/e a lo mass num@er to a@sor@more kinetic ener$y ith each collision and a lo tendency to a@sor@ neutrons so itdoesnt hinder the chain reactionBy*ical materialsE $raphite and aterB

Coolant!oleOHeat is carried from the moderator to the heat e#chan$er @y the coolantB &hepressuriser and the pump mo/e the hot coolant to the heat e#chan$er. here hot coolanttouches pipes carryin$ cold aterB Heat >os from hot coolant to cold ater turnin$ theater into steam and coolin$ the coolantB &he steam then lea/es the reactor Gand ill turna tur@ineI as the coolant return to the reactorB3actors aIecting the choice o= materialsE 7ust @e a@le to carry lar$e amounts of heat

GL11 &he SpecicsI. must @e $as or li9uid. noncorrosi/e. non>amma@le and a poorneutron a@sor@er Gless likely to @ecome radioacti/eIBy*ical materialsOcar@on dio#ide and aterB

Control rods!oleO!or the reactor to transfer ener$y at a constant rate each nuclear ssion reactionmust lead to one more ssion reactionB Since each reaction $i/es out to or more emust remo/e some of the e#tra neutronsB &he control rods a@sor@ neutrons. reducin$ theamount of nuclear ssion processes occurrin$ and makin$ the poer output constantB

&hey can @e loered further into the fuel rods to a@sor@ more neutrons and further reducethe amount of ssion occurrin$B Some neutrons lea/e the reactor ithout interactin$.some tra/el too fast hile other are a@sor@ed @y ?23(nucleiB 'f e need more neutrons ecan raise the control rodsB3actors aIecting the choice o= materialsOA@ility to a@sor@ neutrons and a hi$hmeltin$ pointBy*ical materialsO@oron and cadmiumB

?nit 5

;uclear Safety AspectsLesson *Learnin$

utcomes

&o @e a@le to list and e#plain the safety features of a nuclear reactor

&o @e a@le to e#plain ho an emer$ency shutdon happens in a nuclear reactor

&o @e a@le to state and e#plain the methods of nuclear astedisposal

;B +)="

Nuclear Reactor Saety&here are many safety features and controls in place desi$ned to minimise the risk ofharm to humans and the surroundin$ en/ironmentB

&uel sed?sin$ solids rather than li9uids a/oids the dan$er of leaks or spilla$esB &hey are insertedand remo/ed from the reactor @y remote controlled handlin$ de/icesB

Shielding&he reactor core Gcontainin$ the fuel. moderator and control rodsI is made from steel anddesi$ned to ithstand hi$h temperatures and pressuresB

&he core itself is inside a thick. leak proof concrete @o# hich a@sor@s escapin$ neutronsand $amma radiationB

Around the concrete @o# is a safety area. not to @e entered @y humansB(mergency Shut-down

&here are se/eral systems in place to make it impossi@le for a nuclear disaster to takeplaceE'f the reactor needs stoppin$ immediately the control rods are inserted fully into the core.they a@sor@ any neutrons present and stop any further reactions from happenin$B


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since they are free to slide past each other the potential ener$y is less than that of it insolid formB,asesD 'n a $as particles are free to mo/e in all directions ith hi$h speedsB &here arealmost no forces of attraction @eteen themB &he internal ener$y of a $as is almostentirely due to the kinetic ener$y of the particlesB

Temperature&emperature is a measure of the kinetic ener$ies ofthe particles in the su@stanceB As e can see from the

$raph somethin$ ith a hi$h temperature means theparticles are /i@ratin$mo/in$ ith hi$her a/era$espeeds that a su@stance at a loer temperatureB't is possi@le for to o@:ectssu@stances to @e at thesame temperature @ut ha/e di-erent internalener$iesB )e ill $o into this further in the ne#tlessonE &he SpecicsB

HeatHeat is the >o of thermal ener$y and it >os from a hi$h temperature to a lotemperatureB'f to o@:ects are at the same temperature e say that they are in thermal e9uili@rium

and no heat >osBI% obBect A is in thermal e&uilibrium +ith obBect ! and obBect ! is in thermal e&uilibrium+ith obBect C then A and C must be in thermal e&uilibrium +ith each other$

6et into a hot or cold @ath and ener$y is transferredE'n a cold @ath thermal ener$y is transferred from your @ody to the aterB'n a hot @ath thermal ener$y is transferred from the ater to your @odyB

As the ener$y is transferred you and the ater @ecome the same temperatureB )hen thishappens there is no lon$er a >o of ener$y so no more heatB =ou @oth still ha/e a

temperature due to the /i@rations of your particles @ut there is no lon$er a temperaturedi-erence so there is no lon$er a >o of ener$yB

Temperature Scale&he Celsius scale as esta@lished @y $i/in$ the temperature at hich ater @ecomes icea /alue of , and the temperature at hich it@oils a /alue of 1,,B ?sin$ these #ed points ascale as createdB

A*solute ero and el'ins'n 1(4( )illiam &homson came up ith the8el/in scale for temperatureB He measured thepressure caused @y $ases at knontemperatures Gin CI and plotted the resultsB Hefound a $raph like this oneB


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TmcQ =

cis the specic heat capacity hich is the ener$y re9uired to raise the temperature of 1k$ of a su@stance @y 1 de$reeB 't can @e thou$ht of as the heat ener$y 1 k$ of thesu@stance can hold @efore the temperature ill increase @y 1 de$reeB

&*ecic eat Ca*acity is measured in :oules *er kilogram *er /elvin, :"kg / or :kg1/1

+ater Analogy)e can think of the ener$y @ein$ transferred as /olume of aterB Consider tosu@stancesE one ith a hi$h heat capacity represented @y 25, ml @eakers and one ith a

lo heat capacity represented @y 1,, ml @eakersB )hen a @eaker is full the temperatureof the su@stance ill increase @y 1 de$reeB)e can see that 2 litres of ater ill ll ( of the 25, ml @eakers or 2, of the 1,,ml@eakers meanin$ the same amount of ener$y can raise the temperature of the rstsu@stance @y ( de$rees or the second @y 2, de$reesB

Changes o State)hen a su@stance chan$es state ther

a level physics notes aqa

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