Cambridge A Level Physics 9702 — 2008 Oct/Nov Paper 3 · Variant 1

This document consists of 10 printed pages and 2 blank pages. SPA (KN) T46325/4 © UCLES 2008 [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 6 8 7 2 5 7 4 8 4 * PHYSICS 9702/31 Paper 31 Advanced Practical Skills 1 October/November 2008 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

2 © UCLES 2008 For Examiner’s Use You may not need to use all of the materials provided. 1 In this experiment you will observe the motion of two simple pendulums, and measure the interval between successive times at which the pendulums are moving together. You will investigate how this time interval is affected when the length of one of the pendulums is changed. (a) Set up two simple pendulums side by side as shown in Fig. 1.1, with each string clamped between two wooden blocks. Set the length of pendulum A to about 0.65 m. Pendulum A should be left at its set length throughout the experiment. l B 0.65 m A Fig. 1.1 (b) Adjust pendulum B so that its length l is about 0.5 m. Measure and record the value of l . l = …m 9702/31/O/N/08

3 © UCLES 2008 [Turn over For Examiner’s Use (c) Set both pendulums into motion with small oscillations. Start the stopwatch when the two pendulums are lined up as shown in Fig. 1.2 and are moving in the same direction. side view Fig. 1.2 Determine the time t that elapses before the next occasion when the two pendulums are lined up and moving in the same direction. t = …s 9702/31/O/N/08

4 © UCLES 2008 For Examiner’s Use (d) Change l and repeat (c) until you have six sets of values for l and t. l should be from about 0.3 m to about 0.6 m. Include values of 1–t and 1 l in your table of results. (e) Plot a graph of 1–t on the y-axis against 1 l on the x-axis and draw the line of best fit. (f) Determine the gradient and y-intercept of this line. gradient = … y-intercept = … 9702/31/O/N/08

5 © UCLES 2008 [Turn over For Examiner’s Use 9702/31/O/N/08

6 © UCLES 2008 For Examiner’s Use 9702/31/O/N/08 (g) The equation relating t and l is 1–t = p –– l – p–q where p and q are constants. Use your answer from (f) to determine a value for p. p = …m½s–1 (h) Use your answers from (f) and (g) to determine a value for q. q = …m½

7 © UCLES 2008 [Turn over For Examiner’s Use You may not need to use all of the materials provided. 2 In this experiment you will investigate the resistance of a wire coil. (a) You have been provided with a coil as shown in Fig. 2.1. leads with 4 mm plugs as contacts tape wire insulating tube d Fig. 2.1 (i) Measure and record the diameter d of the insulating tube. d = …m (ii) Estimate the percentage uncertainty in your value for d. percentage uncertainty = … (iii) Use your value from (i) to estimate the length x of wire in a single turn. x = …m 9702/31/O/N/08

8 © UCLES 2008 For Examiner’s Use (b) Set up the circuit as shown in Fig. 2.2, and hold the contacts against two positions on the coil. V A leads with 4 mm plugs as contacts Fig. 2.2 (c) (i) Measure and record the number n of turns between the contacts, voltage V and current I . n = … V = … I = … (ii) Determine the resistance R between the contacts. R = … (iii) The resistance per metre µ of the wire is given by µ = R– x n Use your results to determine a value for µ. µ = … 9702/31/O/N/08

9 © UCLES 2008 [Turn over For Examiner’s Use (d) Repeat (c) for a different value of n. n = … V = … I = … R = … µ = … (e) Explain whether your results support the idea that R is proportional to n. … … … … … 9702/31/O/N/08

10 © UCLES 2008 For Examiner’s Use (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 the experiment. You may suggest the use of other apparatus or different procedures. 1. … … 2. … … 3. … … 4. … … 9702/31/O/N/08

12 BLANK PAGE 9702/31/O/N/08 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 2008 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 2008 9702 31 © UCLES 2008 1 (c) Value of t in range 8 to 18 s. [1] Table (d) Six sets of readings scores 5 marks, five sets scores 4 marks, etc. Write number of sets (ringed) next to table. Help from Supervisor then –1. t should show general increase with l. If not then –1. [5] Repeated readings for t (do not credit if values identical for every row). [1] lmin ≤ 0.35m and lmax ≥ 0.55m. [1] Table headings – every column should have a label and an appropriate unit. [1] Consistency in raw data – all values of t should be given to 0.1 or all given to 0.01s. [1] Check value of 1/√l (for largest l) and tick if correct. [1] Each value of 1/t should be to the same s.f. as (or one more than) the raw value of t. [1] Quality of data – judge from scatter of all plotted points (at least five) about line of best fit. Allow scatter of ±0.025 m –½ in the 1/√l direction. This mark cannot be scored for wrong graph or wrong trend, or if all points have not been plotted. [1] Graph (e) Points should occupy at least half the grid in both directions and scales should be sensible (not 3:10, etc.) and labelled with a quantity. Allow reversed axes. [1] Check that the ‘worst’ point is correctly plotted. This mark cannot be scored unless all data from the table has been plotted – write number of plots (ringed) on the graph. Do not allow blobs (diameter [ half a small square). [1] Line of best fit. Allow five trend plots. [1] (f) Triangle chosen has a hypotenuse at least half the length of the drawn line. Vertices lie on the line and read-offs are correct (to half a small square in both directions) and method of calculation of gradient is correct. Ignore POTE. [1] Intercept calculated using readings from line and a valid method (or read from y-axis provided there is no FO). Ignore any POTE. [1] Conclusions (g) Gradient equated with p. Value of p in range 0.400 to 0.600 m½s–1 inclusive. [1] (h) q calculated starting with ‘intercept value = – p/q’, and correct substitution. q must be opposite sign to intercept unless gradient is negative. [1] [Total: 20]

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – October/November 2008 9702 31 © UCLES 2008 2 (a) (i) Raw value(s) of d recorded to the nearest mm. [1] Repeated readings for d. [1] (ii) Absolute uncertainty of 1 or 2 mm (or half the range) used in a correct percentage uncertainty calculation. [1] (iii) Calculated value of x correct. [1] (c) (i) First value for n. First value for V in range 0.5 Y V Y 2.0. First value for I with I < 1.0 A (unit required). If significant help from Supervisor then –1. [3] (d) Second set of measurements (with different n). [1] Correct calculation of second R. [1] Calculated value of second µ correct (allow e.c.f.). [1] Quality – the two values of µ are within 20% of each other. [1] (This will require a check calculation of first value of µ). Drawing conclusions (e) Valid comment on whether R proportional to n, based on comparison of two calculated ratios (e.g. two values of µ or two values of R/n). Validity can be based on the candidate’s own stated criterion (e.g. ‘values within 10 %’) or, if not stated, on 20 % difference. Accept reversed trend as evidence for R not proportional to n. [1] (f) (i) Problems [4] (f) (ii) Improvements [4] A Two sets of readings are not enough (to draw a conclusion)/only two readings. Take more readings and plot graph. B Tube not circular/tube not rigid. Repeated measurements of d in different directions. C Coils not circular (helix inferred)/different turns have different lengths/wire kinked or loosely wound/x different to πd/turns unevenly spaced. Measure the length in one turn by wrapping string, then unwrapping and measuring/workable method of getting even spacing of turns. D Difficult to judge whole number of turns when positioning contacts/large contact area. Mark lateral line on tube to give positions for contacts/use knife edge contact or smaller plug. E Contact resistance/lead resistance/circuit resistance/fluctuating or changing readings. Measure lead resistance and subtract from R/reposition voltmeter connections closer to contacts/clean the contacts/use shorter leads. F Use vernier calipers to measure d. [Total: 20]