Cambridge A Level Physics 9702 — 2009 May/June Paper 3 · Variant 1

This document consists of 10 printed pages and 2 blank pages. SP (CW/CGW) T73980/3 © UCLES 2009 [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 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 used 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 1 5 7 1 1 1 5 8 6 * PHYSICS 9702/31 Paper 31 Advanced Practical Skills 1 May/June 2009 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/M/J/09 © UCLES 2009 For Examiner’s Use You may not need to use all of the materials provided. 1 In this experiment you will investigate how the current in a circuit depends on the arrangement of resistors within the circuit. You have been provided with four 47 Ω resistors and one unknown resistor. (a) Connect the unknown resistor, labelled X, in series with the four 47 Ω resistors, an ammeter, a battery and a switch, as shown in Fig. 1.1. A 47Ω 47Ω 47Ω X 47Ω Fig. 1.1 Close the switch and record the current I in the circuit. Immediately after taking the reading, open the switch. I = … A

3 9702/31/M/J/09 [Turn over © UCLES 2009 For Examiner’s Use (b) Fig. 1.2 shows a number of possible combinations of the 47 Ω resistors, together with values of their combined resistance R. Resistor arrangement R/Ω 12 16 24 47 71 94 118 141 188 Fig. 1.2

4 9702/31/M/J/09 © UCLES 2009 For Examiner’s Use From Fig. 1.2, select six combinations of resistors. Connect each combination in turn in the circuit of Fig. 1.1, keeping resistor X in the same place. Measure and record the current I for each of your combinations. Include in your table the values of R and 1 I. (c) (i) Plot a graph of 1 I on the y-axis against R on the x-axis. Draw the line of best fit. (ii) Determine the gradient and y-intercept of this line. gradient = … y-intercept = …

5 9702/31/M/J/09 [Turn over © UCLES 2009 For Examiner’s Use

6 9702/31/M/J/09 © UCLES 2009 For Examiner’s Use (d) It is suggested that the relationship between I and R is 1 I = R P + Q P where P and Q are constants. Use your answers from (c)(ii) to determine values for P and Q. Give appropriate units. P = … Q = …

7 9702/31/M/J/09 [Turn over © UCLES 2009 For Examiner’s Use You may not need to use all of the materials provided. 2 In this experiment you will investigate the angle of tilt of a bottle when it contains different amounts of water. (a) (i) Use the water supplied to measure the volume of the bottle. (1 ml = 1 cm3) volume of container = … cm3 (ii) Justify the number of significant figures you have given for the volume of the bottle. … … … (b) Add water to the empty bottle until it is about half-full. (i) Measure the height h as shown in Fig. 2.1. h Fig. 2.1 h = … cm

8 9702/31/M/J/09 © UCLES 2009 For Examiner’s Use (ii) The angle of tilt θ of the bottle is the angle it makes with the horizontal when it is about to topple, as shown in Fig. 2.2. θ Fig. 2.2 Making sure that the lid is secure, tilt the bottle as shown, until it is about to topple, and measure θ. θ = …° (iii) Estimate the percentage uncertainty in θ. percentage uncertainty = … (iv) Measure the volume V of the water in the bottle. V = … cm3

9 9702/31/M/J/09 [Turn over © UCLES 2009 For Examiner’s Use (c) Empty the water from the bottle. Refill the bottle so that it is about a quarter-full and repeat (b)(i), (b)(ii) and (b)(iv). h = … cm θ = … ° V = … cm3 (d) It is suggested that h is inversely proportional to cosθ. Explain whether the results of your experiment support this idea. … … … … …

10 9702/31/M/J/09 © UCLES 2009 (e) (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. … … For Examiner’s Use

12 9702/31/M/J/09 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 May/June 2009 question paper for the guidance of teachers 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, which would have considered the acceptability of alternative answers. 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 May/June 2009 question papers for most IGCSE, GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 2 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9702 31 © UCLES 2009 1 (b) Measurements [6] One mark for each set of readings for different Rtotal 47Ω. Incorrect trend –1 (wrong trend is R ↑ I ↑ / negative gradient). 1 or more incorrect values of R –1. Apparatus setup correctly without help from supervisor. [1] Range of R: to include (12 / 16 Ω) and (71 / 94 Ω) and (141 / 188 Ω). [1] Column headings (R/Ω, I/A, 1/I/A–1). Must have R and 1/I columns. [1] Each column heading must contain a quantity and a unit where appropriate. Ignore units in the body of the table. Do not accept 1/I/ A or 1/I (A). There must be some distinguishing mark between the quantity and the unit (i.e. solidus is expected I/A, but accept, for example, I (A)). Consistency of presentation of raw readings. [1] All values of raw I must be given to the same number of decimal places. Ignore converted current columns. If trailing zeros consistency = 0. If current same consistency = 0. Significant figures [1] Apply to 1/I. If raw I is given to 2 sf, then accept 1/I to 2 or 3 sf. If raw I is given to 3 sf, then accept 1/I to 3 or 4 sf. If raw I is given to 4 sf, then accept 1/I to 4 or 5 sf. Values of 1/I correct. Underline and check a value for 1/I at R = lowest value. [1] If incorrect, write in the correct value. (c) (i) (Graph) Axes. Sensible scales must be used. Awkward scales (e.g. 3:10) are not allowed. [1] Scales must be chosen so that the plotted points must occupy at least half the graph grid in both x and y directions. Indicate false origin with FO. Scales must be labelled with the quantity which is being plotted. Ignore units. All observations must be plotted. Do not accept blobs (points > 0.5 square). [1] Ring and check a suspect plot. Tick if correct. Re-plot if incorrect. Work to an accuracy of half a small square. Line of best fit. Judge by scatter of points about the candidate's line. [1] There must be a fair scatter of points either side of the line. 5 trend points. No kinked lines. Quality. Judge by scatter of all points. All table values need to be plotted. Min 6 needed If wrong trend Q = 0. If any plot out by 10 Ω from examiners line Q = 0. [1] (ii) Gradient [1] The hypotenuse of the ∆ must be equal to or greater than half the length of the drawn line. Read-offs must be accurate to half a small square. Check for ∆y/∆x (i.e. do not allow ∆x/∆y). y-intercept from graph or substitute correct read-offs into y = mx + c. [1] Penalise for incorrect algebra. Label FO.

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9702 31 © UCLES 2009 (d) Correct method for finding P and Q. m = 1/P. c = Q/P [1] Correct method needed. Value for P and Q. Ignore negative sign. [1] P = 1.0 – 5.0 V (or AΩ). Q = 50 – 150 Ω (or V/A) (Resistor X). Unit required. Penalise AE. [Total: 20] Special case: If I same, Measurements = 5 max, Consistency = 0, Axes = 0, Q = 0, Gradient = 0. If no I, consistency = 0, 1/I calculation = 0, SF = 0. Allow CH mark on columns present. 2 (a) (ii) Allow reference to measuring cylinder and consistent number of significant figures. Reference to precision of measuring cylinder. Consistent with SF in their vol. [1] (b) (i) All raw heights to nearest mm. (heights < 30.0 cm) [1] (ii) θ < 90° [1] (iii) Percentage uncertainty in θ. ∆θ = 2 – 5°. [1] If repeated readings have been done then the uncertainty can be half the range. Correct ratio idea required. ∆θ⁄θ (×100%) (×100% can be implied) (c) Measurement of 2nd height less than first height. [1] Measurement of 2nd raw θ (any value) to nearest degree or half a degree [1] Measurement of 2nd volume [1] (c)/(b)(ii) Evidence of repeats in angle measurement [1] θ(b)(ii) > θ(c) [1] (c), (b)(iv) Volume in (c) half of volume in (b)(iv). 0.4 Y Vc/ Vb Y 0.6. [1] (d) Correct calculation to check inverse proportionality. h × cosθ = k [1] One numerical check: check 2nd value if available. Conclusion. Sensible comments relating to calculations to within 20% or their own value and suggested relation. Allow ecf in conclusion if arithmetical error in calculation. If incorrect ideas or no ratio then conclusion = 0. [1] Special case: If 2nd Volume ¾ and not ¼ full, then 2nd Vol = 0 and allow for 2nd height and 2nd angle greater than the first height and first angle respectively.

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE A/AS LEVEL – May/June 2009 9702 31 © UCLES 2009 (e)(i) and (ii) Sources of error or limitation. [4] Improvements. Use of other apparatus or different procedures. [4] Ap Two readings are not enough (to draw a valid conclusion). As Take many (sets of) readings and plot a graph of the results. Be clear NOT just repeat readings. Bp Parallax error in measuring h/θ . Bs Get eye level/‘eye level’ perpendicular (to protractor lines, ruler scale or meniscus). Put scale onto bottle. Cp Difficult to measure height owing to refraction/shape of bottle/thickness of bottom not taken into account/ruler does not start at zero/cannot see meniscus clearly. Cs Add dye/use ruler with a zero at the start. Dp Difficulty in deciding the toppling point. Ds Move by increments/hold with newtonmeter and tilt until F = 0/bottle on tilting ramp idea. Ep Difficulty in measuring θ owing to container not perfectly right angled (curved) at the bottom/difficult to line up protractor/ horizontal line of protractor not on table/ difficult to manipulate bottle and measure angle/flexible container/shape of bottle. Es Make bottom square with plasticine/use protractor with horizontal line flush to table top/freestanding or clamped protractor. [Total: 20] No reference to light gates, motion sensors, video, reaction time, volume measurements, pointers, changing bottle, repeat readings, calipers or movement of container.