Cambridge A Level Physics 9702 — 2007 Oct/Nov Paper 3 · Variant 1

This document consists of 10 printed pages and 2 blank pages. SP (NF/KS) T31602/3 © UCLES 2007 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Subsidiary Level and Advanced Level READ THESE INSTRUCTIONS FIRST Write your Centre number, candidate number and name on all the work you hand in. Write in dark blue or black pen. You may use a soft pencil for any diagrams, graphs or rough working. Do not use staples, paper clips, highlighters, glue or correction fluid. DO NOT WRITE IN ANY BARCODES. Answer both questions. You will be allowed to work with the apparatus for a maximum of one hour for each question. You are expected to record all your observations as soon as these observations are made, and to plan the presentation of the records so that it is not necessary to make a fair copy of them. The working of the answers is to be handed in. Additional answer paper and graph paper should be submitted only if it becomes necessary to do so. You are reminded of the need for good English and clear presentation in your answers. At the end of the examination, fasten all your work securely together. All questions in this paper carry equal marks. * 0 7 6 5 5 6 8 1 9 3 * PHYSICS 9702/31 Paper 31 Advanced Practical Skills 1 October/November 2007 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

2 9702/31/O/N/07 For Examiner’s Use © UCLES 2007 You may not need to use all of the materials provided. 1 In this experiment you will measure the potential difference across a length l of resistance wire joined to a series resistor R. You will use the results of your experiment to determine the current I in the circuit. (a) (i) Use a micrometer to measure the diameter d of the resistance wire. A small section of the wire has been left protruding from the end of the rule for this purpose. d = … (ii) Hence determine the cross-sectional area A of the resistance wire. A = …

3 9702/31/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 (b) (i) Connect the circuit shown in Fig. 1.1. The flying lead X may be placed anywhere along the length of the wire. V l resistance wire R X I Fig. 1.1 (ii) Record the value of the potential difference V and length l of the wire. V = … l = …

4 9702/31/O/N/07 For Examiner’s Use © UCLES 2007 (c) Change the position of X to give a new length l and repeat (a) (ii) until you have six sets of readings for V and l. Include values of l A in your table of results. (d) (i) Plot a graph of V (y-axis) against l A (x-axis). (ii) Draw the line of best fit. (iii) Determine the gradient and the y-intercept of the graph. gradient = … y-intercept = …

5 9702/31/O/N/07 [Turn over For Examiner’s Use © UCLES 2007

6 9702/31/O/N/07 For Examiner’s Use © UCLES 2007 (e) V and l are related by the equation V = lIl A + k where l is the resistivity of the material of the wire, A is the cross-sectional area of the wire and k is a constant. The value of l is given on a card. Using your answers from (d) (iii), determine values for k and I. You should include units where appropriate. k = … I = …

7 9702/31/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 You may not need to use all of the materials provided. 2 In this experiment you will investigate the movement of a loaded rule that is pulled down below its equilibrium position and then released. (a) (i) Mount a loaded metre rule horizontally using a clamp as shown in Fig. 2.1. Fig. 2.1 (ii) Position a metre rule vertically next to the loaded rule as shown in Fig. 2.2. Fig. 2.2

8 9702/31/O/N/07 For Examiner’s Use © UCLES 2007 (iii) Record the equilibrium position of the end of the loaded rule. equilibrium position = … cm (b) Depress the rule so that it is a distance d below the equilibrium position, where 1.0 cm d 5.0 cm. Release the rule. Measure and record the highest position to which the rule rises. Hence determine the distance x, as shown in Fig. 2.3. highest postion equilibrium position position from which rule is released x d Fig. 2.3 d = … cm highest position = … cm x = … cm (c) Estimate the percentage uncertainty in x. percentage uncertainty in x = …

9 9702/31/O/N/07 [Turn over For Examiner’s Use © UCLES 2007 (d) Repeat (b) with a different value of d. d = … cm highest position = … cm x = … cm (e) Do the results of your experiment indicate that x is directly proportional to d within the limits of experimental accuracy? Explain your reasoning clearly. … … … …

10 9702/31/O/N/07 For Examiner’s Use © UCLES 2007 (f) (i) State four sources of error or limitations of the procedure in this experiment. 1. … … 2. … … 3. … … 4. … … (ii) Suggest four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures. 1. … … 2. … … 3. … … 4. … …

12 9702/31/O/N/07 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible. Every reasonable effort has been made by the publisher (UCLES) to trace copyright holders, but if any items requiring clearance have unwittingly been included, the publisher will be pleased to make amends at the earliest possible opportunity. University of Cambridge International Examinations is part of the Cambridge Assessment Group. Cambridge Assessment is the brand name of University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the October/November 2007 question paper 9702 PHYSICS 9702/31 Paper 31 (Advanced Practical Skills 1), maximum raw mark 40 This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. All Examiners are instructed that alternative correct answers and unexpected approaches in candidates’ scripts must be given marks that fairly reflect the relevant knowledge and skills demonstrated. Mark schemes must be read in conjunction with the question papers and the report on the examination. • CIE will not enter into discussions or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the October/November 2007 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9702 31 © UCLES 2007 Question 1 Manipulation, measurement and observation Successful collection of data (a) (i) Diameter of wire. 2 d.p. (mm) in raw data. Allow 0.195 or 0.190 mm. (0.19 mm – 0.02 mm or SV – 0.02 mm). Consistent unit. Unit needed. [1] (i) Repeat measurement [1] (c) 6 measurements in table Five marks for six sets of readings for V and l Four marks for five sets Three marks for four sets, etc. Major or unspecified help –2 (e.g. setting up circuit) Minor help: –1 (e.g. minor changes with circuit) AND –1 (help with reading micrometer) Unreasonable values of V 1 (e.g. Voltage values are the same (Vmax – Vmin < 0.5V ), wrong trend (l
, V) or if any one value of V < 0.5 V.) [5] Range and distribution of values (c) (lmax – lmin) must be greater than or equal to 70 cm. Ignore POT error. [1] Presentation of data and observations Table: layout (c) Column headings: V/V; l/cm; l/A/m–1. [1] Each column heading must contain a quantity and a unit where appropriate. Ignore units in the body of the table. Ignore POT errors. There must be some distinguishing mark between the quantity and the unit (i.e. solidus is expected, but accept, for example, l (cm)). Table: raw data (c) Consistency of presentation of raw readings All values of l must be given to the same number of decimal places. l read to 1 mm or 1 cm [1] Table: calculated quantities (c) Significant figures. Apply to l/A. l/A should be given to the same number or one more than the lowest number of significant figures from l or raw values of d. [1] (c) Values of l/A correct using candidate’s figures. Allow small rounding errors. Check a value. If incorrect, write in the correct value. Ignore POT error. [1]

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9702 31 © UCLES 2007 Graph: layout (Graph) Axes. If wrong graph plotted (e.g. l against l/A) do not award mark. Sensible scales must be used. Awkward scales (e.g. 3:10) are not allowed. Scales must be chosen so that the plotted points occupy at least half the graph grid in both x and y directions. Allow inverted axes. Scales must be labelled with the quantity which is being plotted. Ignore units. [1] Graph: plotting of points (Graph) All observations must be plotted. No blobs (points [ half a small square ). Ring and check a suspect plot. Tick if correct. Re-plot if incorrect. Work to an accuracy of half a small square. [1] Graph: trend line (Graph) Line of best fit. Allow 1 point off. At least 5 trend plots needed. Do not award mark if large scatter. Judge by scatter of points about the candidate’s line. There must be a fair scatter of points either side of the line. Indicate best line if candidate’s line is not the best line. [1] Quality of data (Graph) Judge by scatter of points about the best fit line. Allow up to – 0.05V. All plotted points are assessed for this mark. At least 5 plots needed. If V constant do not award mark. [1] Analysis, conclusions and evaluation Interpretation of graph (d) (iii) Gradient The hypotenuse of the  must be at least half the length of the drawn line. Read-offs must be accurate to half a small square. Do not allow table values unless on the line of best fit. Write in correct read off. Check for
y/
x (i.e. do not allow
x/
y). [1] (d) (iii) y-intercept The value must be read to the nearest half square. The value can be calculated using ratios or y = mx + c. Incorrect algebra –1. If a false origin has been used then label FO. [1] Drawing conclusions (e) Value for k, 0.5 V Y k Y 2.5 V Should be y-intercept. Unit required. 2 or 3 SF. [1] (e) Value for I, 0.05 A Y I Y 0.20 A Must come from gradient. Working must be checked. Unit required A (V–1). 2 or 3SF. Sensible answer checked using candidate’s figures into correct substitution. m=I [1] [Total: 20]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9702 31 © UCLES 2007 Question 2 Manipulation, measurement and observation Successful collection of data (a) (iii) Position of end of rule at equilibrium. Nearest cm or mm. < 1m Consistent unit. [1] (b) First value of d between 1 and 5 cm. If lowest position given write in correct value of d. [1] (b) First value of highest position within 5 cm of the equilibrium position. [1] (d) Second value of d. Different value to the first. Allow out of range. [1] (d) Second value of highest position. [1] (d) Repeated measurements for highest position (evidence from (b) or (d)) [1] Quality of data (d) Bigger d gives bigger x. Check with corrected values of d and x. If d < x in either case or if d = x in both cases, this loses the mark. [1] Presentation of data and observations Display of calculation and reasoning (b) First value of x calculated correctly Calculation must be checked. Write down the correct value if answer wrong. [1] (d) Second value of x calculated correctly Calculation must be checked. Write down the correct value if answer wrong. [1] (e) Correct calculation to check proportionality ecf if candidates value of d is the lowest position. Possibilities include: two calculations of x/d ratio of x values and ratio of d values both calculated [1] Analysis, conclusions and evaluation Drawing conclusions (e) Conclusion based on calculation. Consistent argument. Incorrect ideas score zero. [1] Estimating uncertainties (c) Percentage uncertainty in x Allow uncertainty in x; 2 mm Y x Y 10 mm. If repeated readings have been done then the uncertainty could be half the range. Correct ratio idea required x 100 stated/implied. [1]

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2007 9702 31 © UCLES 2007 Identifying limitations (f) (i) Relevant points must be underlined and ticked. Some of these might be: A Only two readings (are not enough to draw a valid conclusion). B Hard to judge/see (when/where) highest position with reference to movement. Do not accept reaction time ideas. C Parallax (error) or good diagram demonstrating this. D Difficulty in release/keeping rule still prior to release (reference to force). E Equilibrium position changes with evidence shown in measurements. X Other additional source of error. [4] Suggesting improvements (f) (ii) Relevant points must be underlined and ticked.4 Some of these might be: A Take more readings and plot a graph/calculate k values. B High speed (camera to take) photographs/film the motion and play back frame by frame/ slow motion/ use pause OR motion/position sensor above/ below mass OR trial and error with light gate/ horizontal marker. C Measure at eye level/repeat to get eye in right place/ place rule as close as possible to vertical rule/use helper to release or measure/use mounted pin at end of rule (to help locate position on scale). D Use a named method to release the rule e.g. cotton and candle or scissors/electromagnet/end stop or clamp. X cm rule – use a mm rule. Need to see evidence in their previous measurements that their readings are taken to the nearest cm or 0.5 cm. Y Other additional solution, well explained. Do not allow repeated readings, vacuum, draft free room’ Do not allow use a computer to improve the experiment’ Do not allow increase range/change load on ruler/change length of ruler/changing quality of ruler’ [4] [Total: 20]