2010 Physics. Intermediate 2. Finalised Marking Instructions

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1 2010 Physics Intermediate 2 Finalised Marking Instructions Scottish Qualifications Authority 2010 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 = 5 0 Ω (1) Ω (2) Correct answer GMI (1½) Unit missing GMI 2 (a) Ω (0) No evidence/wrong answer GMI 1 5. Ω (0) No final answer GMI 1 V R = = = 4 0 Ω (1½) Arithmetic error GMI 7 I 1 5 V 7. R = = 4 0 Ω 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 (1) Formula + subs/no final answer GMI 4 and V 7 5 R = = = 4 0 I 1 5 (1) Formula + substitution GMI 2 (a) and V 1 5 R = = = 5 0 Ω I 7 5 Formula but wrong substitution GMI V 75 R = = = 5 0 Ω I 1 5 Formula but wrong substitution GMI I 7 5 R = = = 5 0 Ω V 1 5 (0) Wrong formula GMI V = IR 7 5 = 1 5 R R = 0 2 Ω (1½) Arithmetic error GMI V = IR I 1 5 R = = = 0 2 Ω V 7 5 Formula only GMI 20 Page 2

3 2010 Physics Intermediate 2 Marking scheme Section A 1. E 11. B 2. D 12. B 3. B 13. C 4. D 14. A 5. D 15. A 6. C 16. D 7. E 17. C 8. C 18. E 9. D 19. A 10. D 20. E Page 3

4 2010 Physics Intermediate (a) a v u = t 6 0 = 60 = 0 1 m/s 2 (1) 2 (b) s = area under graph = ( ) + (40 6) = 420 m (1) 2 (c) v = t s 420 = 100 = 4 2 m/s (1) 2 (d) W = mg accept 9 8 and 9 81 for g which give 3920 N and 3924 N = = 4000 N (1) 2 (e) F = ma must be consistent with (a) and (d) = = 40 (N) Upward force = = 4040 N (1) 3 Page 4 Total 11

5 22. (a) p before = p after ( ) = v v = 2 5 m/s (1) 2 (b) Direction Air resistance unacceptable: wind resistance friction must be qualified Weight (not gravity) Direction 2 (c) Q = It I = = A (1) 2 (d) Light travels faster than sound (1) 1 Total 7 Page 5

6 23. (a) E h = cm Δ T c = [ (307 ( 173) ] = 899 J/kg C (1) 2 (b) P = E t t = = s (1) 2 (c) (1) 1440 = 200 (rocks) (1) 2 (d) It would be easier (1) Gravitational field strength at the surface of Mercury is less than that at the surface of Earth OR Weight of rocks on Mercury is smaller than their weight on Earth OR Gravity is less on Mercury (1) 2 Total 8 Page 6

7 24. (a) R T = R 1 + R 2 = = 32 Ω (1) V = IR 6 I = 32 I = 0 19 A (1) 3 (b) V 2 = R 2 V S R 1 + R 2 V 2 = V 2 = 1 5 V (1) 2 OR V = IR = = 1 5 V (1) (c) Voltage across 8 Ω resistor would decrease (1) The 8 Ω resistor now has a smaller proportion of the total resistance or less current in the circuit (1) 2 Total 7 Page 7

8 25. (a) a.c. (source) (1) changing magnetic field/current is necessary (to induce voltage) (1) unacceptable: transformers do not work with dc 2 (b) P = IV = = 6 W (1) 2 (c) P = IV = = 5 3 W 1 useful P (d) o percentage efficiency = 100 Pi 5 3 = = 88(%) (1) 2 (e) N S VS = N V P P V S = = 24 V (1) 2 Page 8 Total 9

9 26. (a) Y (n-channel enhancement) MOSFET (1) unacceptable: transistor Z Lamp (1) 2 (b) (Resistance) decreases (1) 1 (c) (As resistance of thermistor decreases) voltage across thermistor decreases. V across X increases When it reaches 1 8V MOSFET V (transistor) switches on Bulb lights and buzzer sounds 2 (d) To allow switch on temperatures to be varied (1) 1 Total 6 Page 9

10 27. (a) s = vt 51 t = 340 = 0 15 s (1) 2 (b) (i) Longitudinal (1) 1 (ii) A transverse wave is one in which the particles vibrate at right angles to the direction of the wave. (1) A longitudinal wave is one in which the particles vibrate parallel to the direction of the wave. (1) 2 (iii) Energy (1) 1 (c) (i) P = V 2 R R = (ii) Any 2 of: = 41 3 Ω (1) 2 independent switching or one off/others stay on (1) to ensure that 315 V is across each bulb (1) if they were in series the necessary voltage would be too high (1) 2 Total 10 Page 10

11 28 (a) (i) v = f λ f = = Hz (1) 2 (ii) T = 1 f 1 T = = s (1) 2 (b) Signals received at same time (1) Radio waves and microwaves have same speed (1) 2 (c) If there are no arrows = 0 for diagram Diagram must have minimum of two rays. All rays drawn must come to a distinct focus or incoming waves are focussed towards one point Curved reflector gives point where energy is maximised (or equivalent) (1) (1) Where there is no diagram: Incoming waves are reflected to a point or focus (1) This maximises the signal at the focus (1) 2 Page 11 Total 8

12 29. (a) A particle containing two protons and two neutrons OR A helium nucleus (1) 1 (b) The gain/loss of electrons by an atom (1) (c) or equivalent (1) = 10 hours (1) 2 (d) A = N t N = = 144,000 (decays) (1) 2 (e) Source may also emit β and/or γ radiation (accept other valid non-standard answer eg neutrons, positrons) (1) 1 Total 7 Page 12

13 30. (a) (i) Slows neutrons (1) 1 (ii) Absorbs neutrons (1) 1 (b) P = E t E = = (J) (1) Numbers of fissions = = (c) Any valid advantage eg much greater energy per kg of fuel compared to other sources OR No greenhouse gases emitted or equivalent (1) These must be relevant to nuclear power and any statements eg dangerous must be qualified Any valid disadvantage eg radioactive waste requires special storage (1) 2 [END OF MARKING INSTRUCTIONS] Page 13 Total 7

2008 Physics. Intermediate 2. Finalised Marking Instructions

2008 Physics. Intermediate 2. Finalised Marking Instructions 2008 Physics Intermediate 2 Finalised Marking Instructions Scottish Qualifications Authority 2008 The information in this publication may be reproduced to support SQA qualifications only on a noncommercial