PHYSICS PHYSICS EXAMINATIONS – 2006EXAMINATIONS – 2006

Bruce WalshBruce Walsh

REMINDERSREMINDERS

CalculatorsCalculators

Study design and textbooksStudy design and textbooks

Examiners report Examiners report

VASS systemVASS system

SSMSSSMS

JUNE EXAMINATIONJUNE EXAMINATION

STATISTICSSTATISTICS

6712 students6712 students

Mean = 90 = 50%Mean = 90 = 50%

Std dev = 38.7 = 21.5%Std dev = 38.7 = 21.5%

Number achieving 100% = 0Number achieving 100% = 0

GRADEGRADE MIN (/180)MIN (/180) MIN (%)MIN (%)

A+A+ 143143 7979

AA 126126 7070

B+B+ 109109 6161

BB 9292 5151

C+C+ 7676 4242

CC 6262 3434

D+D+ 4848 2727

DD 3838 2121

E+E+ 3030 1717

EE 2424 1313

Reasonably challenging paperReasonably challenging paper

Detailed studiesDetailed studies

Attempt ONE detailed study onlyAttempt ONE detailed study only

Explanations address specific question. – Explanations address specific question. – DiagramsDiagrams

Show workingShow working

GENERAL COMMENTSGENERAL COMMENTS

Converting unitsConverting units

Calculations – powers of 10Calculations – powers of 10

- raising to power eg. R- raising to power eg. R33

Care reading scale on axesCare reading scale on axes

Multiple choice questionsMultiple choice questions

Illegible writingIllegible writing

PROBLEM AREASPROBLEM AREASMOTIONMOTION

Q3. Two stage – get acc from F=ma then Q3. Two stage – get acc from F=ma then use const acc formula. Many assumed use const acc formula. Many assumed a=9.8. Few used W=a=9.8. Few used W=ΔΔEEKK

Q6. Net force. Many neglected gravity. Q6. Net force. Many neglected gravity. Others added it instead of subtractingOthers added it instead of subtracting

Q7. Multiple steps. Net force const. Use Q7. Multiple steps. Net force const. Use F=ma for acc then const acc for dist. OR F=ma for acc then const acc for dist. OR I=I=ΔΔp for speed then const acc for dist. p for speed then const acc for dist. Many assumed acc was gMany assumed acc was g

Q8. Two components then Q8. Two components then Pythagoras. Multiple steps Pythagoras. Multiple steps

Q11. I=Q11. I=ΔΔp or get acc then f=ma p or get acc then f=ma Easier to treat space station than Easier to treat space station than shuttle (3shuttle (3rdrd law). Confusion over law). Confusion over masses and speedsmasses and speeds

Q12. Conservation of energy. Some Q12. Conservation of energy. Some fudgingfudging

Q14. Conservation of energy. Loss of Q14. Conservation of energy. Loss of Grav PE = Gain in Spring PE. Many Grav PE = Gain in Spring PE. Many used F=-kx assuming f=mg at used F=-kx assuming f=mg at bottombottom

ELECTRONICS & PHOTONICSELECTRONICS & PHOTONICS

Q1. DC biasing. Parts 2 and 3 poorly doneQ1. DC biasing. Parts 2 and 3 poorly done

Q3. Signal voltage - clippingQ3. Signal voltage - clipping

Q4. Decoupling capacitor. Most knew what Q4. Decoupling capacitor. Most knew what it did but not whyit did but not why

Q8. Modulation Q8. Modulation

RELATIVITYRELATIVITY

Q7-9. Confusion over frames of Q7-9. Confusion over frames of reference.reference.

MATERIALS & STRUCTURESMATERIALS & STRUCTURES

Q3. Reading axis Q3. Reading axis εε=2% not 2=2% not 2

Q4. Calculated wrong material or Q4. Calculated wrong material or misread strain axis misread strain axis

Q6. Work = Area of graph x Volume Q6. Work = Area of graph x Volume Many forgot volume or had Many forgot volume or had calculation difficultiescalculation difficulties

FURTHER ELECTRONICSFURTHER ELECTRONICS

Q7. Operation of regulatorQ7. Operation of regulator

NOVEMBER NOVEMBER EXAMINATIONEXAMINATION

STATISTICSSTATISTICS

6589 students6589 students

Mean = 111 = 62%Mean = 111 = 62%

Std dev = 41 = 23%Std dev = 41 = 23%

Number achieving 100% = 20Number achieving 100% = 20

GRADEGRADE MIN (/180)MIN (/180) MIN (%)MIN (%)

A+A+ 162162 9090

AA 150150 8383

B+B+ 134134 7474

BB 115115 6464

C+C+ 9898 5454

CC 8282 4646

D+D+ 6666 3737

DD 5050 2828

E+E+ 3636 2020

EE 3030 1717

GENERAL COMMENTSGENERAL COMMENTS

Accessible paperAccessible paper

Detailed studiesDetailed studies

Illegible writingIllegible writing

Explanations must address specific Explanations must address specific questionquestion

Explanations – one mark per pointExplanations – one mark per point

Show workingShow working

Unit conversions, eg. cmUnit conversions, eg. cm22 to m to m22

Read questions carefully. Answer Read questions carefully. Answer what is asked not what you expect to what is asked not what you expect to be asked.be asked.

PROBLEM AREASPROBLEM AREASELECTRIC POWERELECTRIC POWER

Q1. Sketching magnetic fields.Q1. Sketching magnetic fields.

Q8. E.M. induction. Trouble calculating area Q8. E.M. induction. Trouble calculating area (units) and getting correct time(units) and getting correct time

Q14-15. Operation of transformer Q14-15. Operation of transformer

Q16. Overall distribution systemQ16. Overall distribution system

LIGHT and MATTERLIGHT and MATTER

Q1. Incoherent light from wide Q1. Incoherent light from wide spectrum sources. Confused with spectrum sources. Confused with discrete emission spectrum.discrete emission spectrum.

Q2. Wave and particle predictions for Q2. Wave and particle predictions for PE effect.PE effect.

Q6. Meaning of standing waves for Q6. Meaning of standing waves for electrons in stable states in atoms.electrons in stable states in atoms.

Q11. Distinction between matter and Q11. Distinction between matter and electromagnetic radiation. Wrong electromagnetic radiation. Wrong Planck’s constant. Assumption that Planck’s constant. Assumption that because momentum was the same, because momentum was the same, energy was also. Electron speed energy was also. Electron speed taken as 3x10taken as 3x1088..

SYNCHROTRONSYNCHROTRON

Q2. Q2. ExplainExplain two advantages. two advantages.

Q5. Relate greater wavelength to Q5. Relate greater wavelength to reduced energy.reduced energy.

PHOTONICSPHOTONICS

Q5. Operation of graded index Q5. Operation of graded index multimodal fibresmultimodal fibres

Q6-7. Snell’s lawQ6-7. Snell’s law

Q10. Rayleigh scattering increases as Q10. Rayleigh scattering increases as wavelength decreases.wavelength decreases.

SOUNDSOUND

Q6. Sound from front and rear out of Q6. Sound from front and rear out of phase, box prevents interference.phase, box prevents interference.

Q9. Unable to explain resonance in Q9. Unable to explain resonance in terms of behaviour of sound waves.terms of behaviour of sound waves.