PHYSICS EXAMINATIONS 2006 Bruce Walsh REMINDERS u Calculators

PHYSICS EXAMINATIONS – 2006 Bruce Walsh

REMINDERS u Calculators u Study design and textbooks u Examiners report u VASS system u SSMS

JUNE EXAMINATION

STATISTICS u 6712 students u Mean = 90 = 50% u Std dev = 38. 7 = 21. 5% u Number achieving 100% = 0

GRADE A+ A B+ B C+ C D+ D E+ E MIN (/180) 143 126 109 92 76 62 48 38 30 24 MIN (%) 79 70 61 51 42 34 27 21 17 13

GENERAL COMMENTS u Reasonably challenging paper u Detailed studies u Attempt ONE detailed study only u u Explanations address specific question. – Diagrams Show working

u u Converting units Calculations – powers of 10 - raising to power eg. R 3 u Care reading scale on axes u Multiple choice questions u Illegible writing

PROBLEM AREAS MOTION u u u Q 3. Two stage – get acc from F=ma then use const acc formula. Many assumed a=9. 8. Few used W=ΔEK Q 6. Net force. Many neglected gravity. Others added it instead of subtracting Q 7. Multiple steps. Net force const. Use F=ma for acc then const acc for dist. OR I=Δp for speed then const acc for dist. Many assumed acc was g

u u u Q 8. Two components then Pythagoras. Multiple steps Q 11. I=Δp or get acc then f=ma Easier to treat space station than shuttle (3 rd law). Confusion over masses and speeds Q 12. Conservation of energy. Some fudging

u Q 14. Conservation of energy. Loss of Grav PE = Gain in Spring PE. Many used F=-kx assuming f=mg at bottom

ELECTRONICS & PHOTONICS u Q 1. DC biasing. Parts 2 and 3 poorly done u Q 3. Signal voltage - clipping u u Q 4. Decoupling capacitor. Most knew what it did but not why Q 8. Modulation

RELATIVITY u Q 7 -9. Confusion over frames of reference.

MATERIALS & STRUCTURES u u u Q 3. Reading axis ε=2% not 2 Q 4. Calculated wrong material or misread strain axis Q 6. Work = Area of graph x Volume Many forgot volume or had calculation difficulties

FURTHER ELECTRONICS u Q 7. Operation of regulator

NOVEMBER EXAMINATION

STATISTICS u 6589 students u Mean = 111 = 62% u Std dev = 41 = 23% u Number achieving 100% = 20

GRADE A+ A B+ B C+ C D+ D E+ E MIN (/180) 162 150 134 115 98 82 66 50 36 30 MIN (%) 90 83 74 64 54 46 37 28 20 17

GENERAL COMMENTS u Accessible paper u Detailed studies u Illegible writing u Explanations must address specific question

u Explanations – one mark per point u Show working u Unit conversions, eg. cm 2 to m 2 u Read questions carefully. Answer what is asked not what you expect to be asked.

PROBLEM AREAS ELECTRIC POWER Q 1. Sketching magnetic fields. Q 8. E. M. induction. Trouble calculating area (units) and getting correct time Q 14 -15. Operation of transformer Q 16. Overall distribution system

LIGHT and MATTER u u u Q 1. Incoherent light from wide spectrum sources. Confused with discrete emission spectrum. Q 2. Wave and particle predictions for PE effect. Q 6. Meaning of standing waves for electrons in stable states in atoms.

u Q 11. Distinction between matter and electromagnetic radiation. Wrong Planck’s constant. Assumption that because momentum was the same, energy was also. Electron speed taken as 3 x 108.

SYNCHROTRON u u Q 2. Explain two advantages. Q 5. Relate greater wavelength to reduced energy.

PHOTONICS u u u Q 5. Operation of graded index multimodal fibres Q 6 -7. Snell’s law Q 10. Rayleigh scattering increases as wavelength decreases.

SOUND u u Q 6. Sound from front and rear out of phase, box prevents interference. Q 9. Unable to explain resonance in terms of behaviour of sound waves.