2015 Physics. Higher (Revised) Finalised Marking Instructions

Transcription

1 05 Physics Higher (Revised) Finalised Marking Instructions Scottish Qualifications Authority 05 The information in this publication may be reproduced to support SQA qualifications only on a non-commercial basis. If it is to be used for any other purposes written permission must be obtained from SQA s NQ Assessment team. 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 NQ Assessment team 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 Part One: General Marking Principles for Physics Higher (Revised) This information is provided to help you understand the general principles you must apply when marking candidate responses to questions in this Paper. These principles must be read in conjunction with the specific Marking Instructions for each question. (a) (b) Marks for each candidate response must always be assigned in line with these general marking principles and the specific Marking Instructions for the relevant question. If a specific candidate response does not seem to be covered by either the principles or detailed Marking Instructions, and you are uncertain how to assess it, you must seek guidance from your Team Leader/Principal Assessor. Marking should always be positive ie, marks should be awarded for what is correct and not deducted for errors or omissions. GENERAL MARKING ADVICE: Physics Higher (Revised) The marking schemes are written to assist in determining the minimal acceptable answer rather than listing every possible correct and incorrect answer. The following notes are offered to support Markers in making judgements on candidates evidence, and apply to marking both end of unit assessments and course assessments.. General Marking Instructions SQA published Physics General Marking Instructions in July 999. Please refer to this publication when interpreting the detailed Marking Instructions.. Recording of marks The following additional advice was given to markers regarding the recording of marks on candidate scripts. (a) (b) (c) (d) The total mark awarded for each question should be recorded in the outer margin. The inner margin should be used to record the mark for each part of a question as indicated in the detailed Marking Instructions. The fine divisions of marks shown in the detailed Marking Instructions may be recorded within the body of the script beside the candidate s response. Where such marks are shown they must total to the mark in the inner margin. Numbers recorded on candidate scripts should always be the marks being awarded. Negative marks or marks to be subtracted should not be recorded on scripts. The number out of which a mark is scored should never be recorded as a denominator. (½ mark will always mean one half mark and never out of ) Page

3 (e) (f) (g) Where square ruled paper is enclosed inside answer books it should be clearly indicated that this item has been considered by the marker. The mark awarded should be transferred to the script booklet inner margin and marked G. The mark awarded for each question should be transferred to the grid on the back of the script. When the marker has completed marking the candidate s response to all questions, the marks for individual questions are added to give the total script mark. The total mark awarded for an individual question may include an odd half mark ½. If there is an odd half mark in the total script mark, this is rounded up to the next whole number when transferred to the box on the front of the script. 3. Other Marking Symbols which may be used TICK Correct point as detailed in scheme, includes data entry SCORE THROUGH Any part of answer which is wrong. (For a block of wrong answers indicate zero marks.) INVERTED VEE A point omitted which has led to a loss of marks. WAVY LINE Under an answer worth marks which is wrong only because a wrong answer has been carried forward from a previous part. G Reference to a graph on separate paper. You MUST show a mark on the graph paper and the SAME mark on the script. 4. Marking Symbols which may NOT be used. WP Marks not awarded because an apparently correct answer was due to the use of wrong physics. ARITH Candidate has made an arithmetic mistake. SIG FIGS or SF Candidate has made a mistake in the number of significant figures for a final answer. Page 3

4 Physics Marking Issues The current in a resistor is 5 amperes when the potential difference across it is 7 5 volts. Calculate the resistance of the resistor. Answers Mark +comment Issue. V=IR 7 5= 5R R=5 0 () Ideal Answer. 5 0 () Correct Answer GMI (½) Unit missing GMI (a) (0) No evidence/wrong Answer GMI 5. (0) No final answer GMI V 7 5 (½) Arithmetic error GMI 7 6. R= = =4 0 I 5 7. R= I V =4 0 Formula only GMI 4 and 8. R= I V = Formula only GMI 4 and V 7 5 () Formula + subs/no final answer GMI 4 and 9. R= = = I 5 V 7 5 () Formula + substitution GMI (a) and 7 0. R= = =4 0 I 5 V 5 Formula but wrong substitution GMI 5. R= = =5 0 I 7 5 V 75 Formula but wrong substitution GMI 5. R= = =5 0 I 5 I 7 5 (0) Wrong formula GMI 5 3. R= = =5 0 V 5 4. V=IR 7 5 = 5 R R=0 (½) Arithmetic error GMI 7 5. V=IR I 5 Formula only GMI 0 R= = =0 V 7 5 Page 4

5 Part Two: Marking Instructions for each Question 05 Physics Higher (Revised) Section A Question Expected Answer(s) Max Mark Question Expected Answer(s) Max Mark. C. A. B. D 3. C 3. D 4. E 4. B 5. C 5. A 6. E 6. E 7. B 7. B 8. D 8. E 9. A 9. E 0. D 0. D Page 5

6 Section B: Question Sample Answers and Mark Allocation Notes Inner Outer a i A v = 6 m s () Deduct for wrong or missing units 8 B v h = 6 cos 40 = 8 9 m s () (accept 8 886, 8 89, 9 not 9 0) or consistent with A C v v = 6 sin 40 = 7 5 m s () (accept 7 456, 746, 7, not 7 0) or consistent with A a ii A s ut at 47 = 0 + ½ 9 8 t = Total Time = = 7 s not secs (accept, 74, 739) Alternative: v = u + a s = v = 9 6 v = u + at 9 6 = t t = Total t = = 7 s s and a must have same sign Accept but not 0 B d v t d 89 7 d = 5 m () Or consistent with (a)(ii)(a) and (a)(i)(b) 74 is ok for t, giving d = 5, 5 5 or 5 49 (accept 5, 5 3) b (total energy remains the same) the greater the angle the more energy used to lift the put to a greater height before release less energy available to convert to E k Kinetic energy is less This statement is required before any marks awarded. (The release) speed is less (A) Page 6

7 a v u a s 0 90 a 980 a ms Independent calculations If 000 for s, max () u and s must have the same sign 3 (3A) 5 F ma 700N Negative sign missing subtract w mg N If drop negative sign from line to line 3 subtract Force exerted by engines = = 600 N If final answer is 500 N then student used s = 000, max () b (Constant speed ) upward force = weight 3 Tcos0 = 380 (½) Or forces are balanced (A) T = 490 (N) If T = 490 (N) not shown, then max (½) Page 7

8 3 a i Ft = mv mu F 0 00 = = 30 N () (accept 3 N) Or v = u + at 39 = 0 + a 0 00 a = 950 F = ma = Both formulae Both substitutions F = 3 N () Wrong or missing unit in final answer, deduct 5 a ii At least one labelled axis is F required, otherwise (0) 0 t Then, correct shape of graph () If peak labelled as 30 N, deduct. If peak labelled as occurring at 0 0 s, deduct If no label on origin, subtract b lower peak () F longer time () first ball second ball Graphs not identified (0) Ignore areas being different. (A) 0 t Page 8

9 4 Demonstrates no understanding (0) Limited understanding () Reasonable understanding () Good understanding (3) This is an open-ended question. mark: The student has demonstrated a limited understanding of the physics involved. The student has made some statement(s) which is/are relevant to the situation, showing that at least a little of the physics within the problem is understood. Open ended question a variety of Physics arguments can be used to answer this question. Marks are awarded on the basis of whether the answer, overall, demonstrates no, limited, reasonable or good understanding. 3 (A) 3 marks: The student has demonstrated a reasonable understanding of the physics involved. The student makes some statement(s) which is/are relevant to the situation, showing that the problem is understood. 3 marks: The maximum available mark would be awarded to a student who has demonstrated a good understanding of the physics involved. The student shows a good comprehension of the physics of the situation and has provided a logically correct answer to the question posed. This type of response might include a statement of the principles involved, a relationship or an equation, and the application of these to respond to the problem. This does not mean the answer has to be what might be termed an excellent answer or a complete one. Page 9

10 5 a photons of particular/some/certain energies/frequencies are absorbed in the Sun s (upper/outer) atmosphere Or, particular/certain frequencies/wavelengths of light are absorbed the atmosphere is too vague 7 b i Light is redshifted/shifted towards red (as) the galaxies are moving away (from the Sun) b ii z = (λ o λ r ) / λ r = ( )/ = Or, the wavelength has increased Not: blueshift / becomes red / shifted to red these are wrong physics, award 0 marks. Or distant galaxy has greater recessional velocity Must start with the appropriate relationship Award a maximum of mark if final answer is not b iii v = zc = = m s d = v/h o = ( )/( ) = m () (= ly ) This mark anywhere If z is not 0 098, then incorrect substitution. This mark anywhere (accept 8 0 5, ) There is no need to convert to light years but if done, it must be correct, otherwise max () marks 3 (3A) c The redshift is greater for the distant galaxy, meaning that the distant galaxy is moving away faster than the nearby galaxy () Page 0

11 6 a Photon () 4 b i 6 GeV = ( ) () = (J) m = E/c = / ( ) (= ) = 0 5 (kg) This conversion must be clearly shown somewhere in the answer This mark anywhere Deduct if 0 5 not shown as the final line b ii ( 0 5 / =) 34 (Higgs boson is) orders of magnitude bigger (approx.) 00 If mass of neutron ( ) is used, treat as wrong physics award zero marks. 34 times bigger, only (A) 7 a i (some) mass is converted into energy () mass is lost on its own gets 5 mass is changed is insufficient a ii The thorium nucleus will have some of the (kinetic) energy () or is also emitted lost as heat/sound energy is wrong physics, award zero marks (A) b i scandium () or Sc b ii (an extra particle) the (anti)neutrino () would have (some kinetic) energy () another particle also emitted gets Page

12 8 Demonstrates no understanding (0) Limited understanding () Reasonable understanding () Good understanding (3) This is an open-ended question. mark: The student has demonstrated a limited understanding of the physics involved. The student has made some statement(s) which is/are relevant to the situation, showing that at least a little of the physics within the problem is understood. Open ended question a variety of Physics arguments can be used to answer this question. Marks are awarded on the basis of whether the answer, overall, demonstrates no, limited, reasonable or good understanding. 3 (A) 3 marks: The student has demonstrated a reasonable understanding of the physics involved. The student makes some statement(s) which is/are relevant to the situation, showing that the problem is understood. 3 marks: The maximum available mark would be awarded to a student who has demonstrated a good understanding of the physics involved. The student shows a good comprehension of the physics of the situation and has provided a logically correct answer to the question posed. This type of response might include a statement of the principles involved, a relationship or an equation, and the application of these to respond to the problem. This does not mean the answer has to be what might be termed an excellent answer or a complete one. Page

13 9 a i Different frequencies / colours are refracted through different angles () OR different frequencies / colours have different refractive indices () Not wavelength on its own but ignore if reference made to frequency. Do NOT accept bending on its own but ignore it if follows refraction A correct answer followed by diffract or defract, 0 marks 8 a ii v n v v v ms 8 () (accept 9, 948, 948) b i v = f λ = λ 3 (A) λ = m λ = d sinθ = d sin 9 d = m () b ii different colours have different λ mλ = dsinθ m and d are the same θ is different for different λ OR different colours have different λ Path difference = mλ for the same m PD is different for different λ Any answer using different colours/ wavelengths diffract different amounts as the explanation is wrong physics award 0 marks (A) Page 3

14 Question Sample Answers and Mark Allocation Notes Inner Margin Outer Margin 30 a i R V / I R total lamp 45 / total R 5 05 OR E = IR + Ir 4 5 = 0 3 R R = 4 5 R lamp =4 5 5 = Ω Lose if last line not shown 9 a ii P = I R = 0 30 = W () (accept 08 W) OR, V = IR = 0 3 (= 3 6 ) Need the above before any marks can be awarded for the next line P = IV = = W () b i 3 5 V () Deduct for a wrong or missing unit. b ii E = V + Ir 4 5 = V Or consistent with (b)(i) V = 4 4 (V) V Rv = = 0 9 V c (when a) current or electrons move passes through a p-n junction photons are emitted () light emitted Page 4

15 3 a Q CV C Must start with the relationship deduct if Q = 0 6 (C) not shown 5 E b QV J OR E CV J () () must be 0 6, cannot carry a wrong answer from (a) OR E = ½ Q /C = ½ 0 6 /3 0 6 = 400 J () c I = V/R 5000 / 40 5A () (A) Page 5

16 3 a (vertically) into the page not down(wards), but down into the page is ok 8 b i Correct drawing of axes, plotting of points and drawing a smooth curve () A non-linear scale on either axis is wrong Physics and prevents access to any marks Any quantity or unit missing from labels, off per axis, but the labelling of the origin is not required in this answer. Penalise here if power of 0 is missing. b ii gradient = y y / x x = ( )/(450 0) = (m T) or (T m) points must be on graph line Unit not required, but if wrong unit max b iii mv gradient Q v = gradient Q/m (A) / 9 0 () = m s - () c Set/measure speed v (of electron) measure radius r keep B constant repeat for different v [END OF MARKING INSTRUCTIONS] Page 6