2012 Physics. Intermediate 2. Finalised Marking Instructions

Transcription

1 01 Physics Intermediate Finalised Marking Instructions Scottish Qualifications Authority 01 The information in this publication may be reproduced to support SQA qualifications only on a noncommercial basis. If it is to be used for any other purposes written permission must be obtained from the External Print Team, Centre Services, Dalkeith. Where the publication includes materials from sources other than SQA (secondary copyright), this material should only be reproduced for the purposes of examination or assessment. If it needs to be reproduced for any other purpose it is the centre s responsibility to obtain the necessary copyright clearance. SQA s External Print Team, Centre Services, at Dalkeith may be able to direct you to the secondary sources. These Marking Instructions have been prepared by Examination Teams for use by SQA Appointed Markers when marking External Course Assessments. This publication must not be reproduced for commercial or trade purposes.

2 Physics Marking Issues The current in a resistor is 1 5 amperes when the potential difference across it is 7 5 volts. Calculate the resistance of the resistor. Answers Mark + Comment Issue 1. V = IR Ideal answer 7 5 = 1 5R R = () Correct answer GMI (1½) Unit missing GMI (a) (0) No evidence/wrong answer GMI 1 5. (0) No final answer GMI 1 V R 4 0Ω (1½) Arithmetic error GMI 7 I 1 5 V 7. R 4 0Ω Formula only GMI 4 and 1 I V 8. R Ω Formula only GMI 4 and 1 I 9. V 7 5 R I 1 5 Ω Formula + subs/no final answer GMI 4 and V 7 5 R 4 0 I 1 5 Formula + substitution GMI (a) and V 1 5 R 5 0Ω I 7 5 Formula but wrong substitution GMI 5 1. V 75 R 5 0Ω I 1 5 Formula but wrong substitution GMI I 7 5 R 5 0Ω V 1 5 (0) Wrong formula GMI V = IR 7 5 = 1 5 R R = 0 (1½) Arithmetic error GMI V = IR I 1 5 R 0 Ω V 7 5 Formula only GMI 0 Page

3 01 Physics Intermediate Marking scheme Section A 1. D 11. D. A 1. A 3. D 13. B 4. B 14. D 5. C 15. D 6. A 16. E 7. C 17. C 8. B 18. C 9. C 19. E 10. A 0. E Page 3

4 01 Physics Intermediate Sample Answer and Mark Allocation Marks 1. (a) (i) d vt 8, Mins not converted to s, deduct ½ 49,800,000m (ii) (As orbit is circular) direction changes / or unbalanced force exists so velocity changes. (b) d vt Anything other than stop marking ( ½ for formula) Wrong conversion of 800 km deduct ½ ,000,000 t and OK t s (c) (i) The weight of 1 kg OR Weight per unit mass OR Earth s pull per kg. Weight/mass = 0; force per unit mass = 0; Newtons per kg = 0; Gravity per kg = 0; same as 10m/s = 0 1 (ii) 7.8 N/kg No tolerance exact value required. Minus ½ for missing/wrong unit. 1 (iii) W mg Must use the same value as stated in part (ii) OR correct value N s.f. accept 655.; 655; 700 Page 4

5 . (a) Car continues at a constant speed during this time. AB represents driver s reaction time OR the forces are balanced (or equivalent). Must describe constant speed to get second mark (b) 1 E mv If 30 without squaring symbol is used stop marking. 315,000J J OK (c) 315,000J Answer must be consistent with (b) 1 Page 5

6 (d) v u a t ( 0 30)/.5 ( 30 0)/. 5 OR ( )1 (m/s ) If used = minus ( ½ ).. F ma N If F = 8400 N not stated minus ½ OR d area under graph a.u.g. or implied OR 37.5(m).. E W Fd 315,000 F 37.5 If F = 8400 N not stated minus ½ F 8400N Page 6 Total 7

7 3. (a) (i) E P mgh Accept g = 9.8 ; 9.81; s.f. accept more or 1 less 96.5 J 97 J OK (ii) E H cm T T E H must be consistent with (i). If any other value of c used, only for formula. T 0.5 C (iii) Less than. Some heat is lost to surroundings/ or equivalent. If less than is on its own = 0 marks. Less than plus wrong explanation = 1 mark. Heat loss to must be qualified. Qualified sound loss OK eg on hitting the ground (b) E h ml ( ) If wrong value from same table for latent heat of fusion used = minus 1. Any other value used = ( ½ ) for formula. 10,500J J, J OK 3 Total 9 Page 7

8 4. (a) mark each symbol () for position of each meter (voltmeter across battery = OK) One cell drawn - unacceptable 6V label not needed 3 (b) V IR R R Ω OK (c) P VI or P = I R OK P Values must be consistent with (b). P 3.4 W This is greater than the 3W or labelled power rating (so it overheats). 3 Page 8

9 (d) No ( ½ ) NO on its own = ( ½ ) In parallel the voltage is still the same/6v across each resistor So power is the same (OR correct calculations) Total 10 Page 9

10 5. (a) MOSFET Transistor on its own = 0 Correct spelling required 1 (b) (Voltage) falls/decreases Or equivalent Arrows not allowed 1 (c) (i) V 1 Substitution for V 1 must be consistent with (i) or the correct value. (ii) V1 R1 V I for equation once V R R V R 9.6 I 5600 R 1400 ( I ) V R T I R T If incorrect substitution in either equation, stop marking. R 1400 T Page 10

11 (d) (Lamp) stays on only if explanation attempted even if there is wrong physics (Temperature falls) R T rises Arrows not acceptable V T rises V T.4 V or switching voltage Total 7 Page 11

12 6. (a) (i) Speed of sound (much) less than speed of light (or similar) 1 (ii) d vt 176 v 0.5 v 35m/s s.f. 350, 400 OK (b) The current creates a magnetic field around the coil OR The contact is attracted to the magnetic coil. The steel contact is attracted by the (magnetised) coil/core (c) V R 9 6 3V Subtraction of 6 from 9 must be attempted. No subtraction max ( ½ ) for formula... V IR R R 3.75 s.f. 4, 3.8 OK 3 (d) v f No other value for speed allowed. 0.4 m Page 1 Total 10

13 7. (a) Greater Accept bigger, larger, longer but not higher 1 (b) Angle of incidence Normal Angle of refraction for each correct label ( 1 ) The normal must be drawn correctly (PJ) to allow marks to be given for labelling marks. Accept i, r and N for correct change of direction Arrows not required. (c) Total internal reflection Accept TIR 1 Total 4 Page 13

14 8. (a) Correct reflection of straight rays Arrows essential and minimum of 3 rays required. Arriving at (labelled) microphone at focus (b) More energy OR power OR amplitude is received (at the microphone.) Do not accept there are more signals, stronger /amplified signal, concentrated sound or more waves at the microphone. Focusing the sound waves OK 1 (c) V o Vgain Vi 3 V gain 0.04 If 4 used answer 0.15 treat as arithmetical error (1½ max) If unit given (-½) V 15 gain (d) (i) Short sight 1 (ii) Diverging/concave or diagram OK If long sight answered in (i) then accept convex/converging lens for (ii). (max 1 mark) 1 Page 14

15 (e) 1 P f 1 10 f f 0.1m (10cm) Total 9 Page 15

16 9. (a) Any two correct count rate values from the graph, i.e. second = half of the first. Half-life = hours Weapons, atmosphere, rocks etc must be qualified in terms of radioactivity. PJ (b) Any two valid answers. for each (c) A type of electromagnetic radiation / wave/ ray. Don t accept EM 1 Total 5 Page 16

17 30. (a) (i) D E / m Wrong conversion of a unit (- ½ ) / Gy 1. x 10-5 or 1 µgy (ii) H Dw R D must be consistent with (i) or correct value used Sv.4 x 10-4 ; 40 µsv or 0.4 msv (iii) A N / t 4,000/(5 60) 80Bq (b) (i) The moderator slows neutrons. (ii) The containment vessel prevents/reduces release of radiations OR radioactive gases OR radioactive substances etc. Do not accept the release of radioactivity. (c) Fission or Chain reaction. Do not accept fussion. Fision OK. 1 Total 10 [END OF MARKING INSTRUCTIONS] Page 17