Cambridge A Level Physics 9702 — 2010 May/June Paper 3 · Variant 2

This document consists of 9 printed pages and 3 blank pages. DC (KN/CGW) 15325/5 © UCLES 2010 [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. You may lose marks if you do not show your working or if you do not use appropriate units. 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. * 3 8 2 3 4 2 1 5 0 0 * PHYSICS 9702/32 Paper 32 Advanced Practical Skills 2 May/June 2010 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

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3 [Turn over 9702/32/M/J/10 © UCLES 2010 For Examiner’s Use You may not need to use all of the materials provided. 1 In this experiment, you will measure the current through a set of resistors. (a) (i) Connect the circuit of Fig. 1.1, ensuring that the movable lead is connected between resistors 1 and 2. Z 1 2 3 A Fig. 1.1 (ii) Close the switch and record the ammeter reading I. Open the switch after recording your measurement. I = … A

4 9702/32/M/J/10 © UCLES 2010 For Examiner’s Use (b) By adjusting the movable lead, the resistor Z may be connected in series with a number N of other resistors. Each of the resistors labelled 1 to 12 has a resistance of 22 Ω. Repeat (a)(ii) for different values of N until you have six sets of readings for N and I. Include in your table of results values of 1–I and the total resistance R of the 22 Ω resistors connected into the circuit. (The total resistance R of the 22 Ω resistors in series can be determined using the formula R = R1 + R2 + R3 + … ) (c) (i) Plot a graph of R on the y-axis against 1–I on the x-axis. (ii) Draw the line of best fit. (iii) Determine the gradient and y-intercept of the line of best fit. gradient = … y-intercept = …

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6 9702/32/M/J/10 © UCLES 2010 For Examiner’s Use (d) The quantities R and I are related by the equation R = G ––I + H where G and H are constants. Use your answers to (c)(iii) to determine values for G and H. You should include units where appropriate. G = … H = …

7 [Turn over 9702/32/M/J/10 © UCLES 2010 For Examiner’s Use You may not need to use all of the materials provided. 2 In this question, you will investigate how the attractive force between two magnets depends on their separation. (a) You are provided with a pair of magnets, one of which is fixed to the bench. You are also provided with some microscope slides, adhesive tape, a loop of cotton and a newton meter. You also have access to a micrometer screw gauge. (i) Place the loop of cotton around the magnet that is not fixed, as shown in Fig. 2.1, and use the adhesive tape to secure the cotton to the sides. loop of cotton adhesive tape Fig. 2.1 (ii) Place the magnet with the loop of cotton end-to-end with the fixed magnet, so that they are attracting, as shown in Fig. 2.2. fixed magnet Fig. 2.2

8 9702/32/M/J/10 © UCLES 2010 For Examiner’s Use (b) (i) Using the newton meter, measure the maximum force F required to pull the magnets apart, as shown in Fig. 2.3. fixed magnet newton meter Fig. 2.3 F = … N (ii) Explain why it is difficult to determine this force accurately. … … … (iii) Estimate the percentage uncertainty in the maximum force required to separate the attracting magnets. Show all your working. percentage uncertainty = … (c) (i) Using the micrometer screw gauge, measure the total thickness t of three of the microscope slides, as shown in Fig. 2.4. t Fig. 2.4 t = … mm (ii) Explain how you have made this measurement as accurate as possible. … … …

9 [Turn over 9702/32/M/J/10 © UCLES 2010 For Examiner’s Use (iii) Place the three slides between the two attracting magnets, as shown in Fig. 2.5. Use the newton meter to find the maximum force F needed to separate the magnets. t Fig. 2.5 F = … (d) Repeat (c)(i) and (c)(iii) for a single slide placed between the attracting magnets. t = …mm F = … (e) It is suggested that F and t are related by the equation F = k––t where k is a constant. By calculating values of k, explain whether your results support this relationship. … … … …

10 9702/32/M/J/10 © UCLES 2010 For Examiner’s Use (f) (i) Describe four sources of uncertainty or limitations of the procedure in this experiment. 1. … … 2. … … 3. … … 4. … … (ii) Describe four improvements that could be made to this experiment. You may suggest the use of other apparatus or different procedures. 1. … … 2. … … 3. … … 4. … …

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12 9702/32/M/J/10 © UCLES 2010 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 2010 question paper for the guidance of teachers 9702 PHYSICS 9702/32 Paper 32 (Advanced Practical Skills), 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 2010 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 AS/A LEVEL – May/June 2010 9702 32 © UCLES 2010 1 (b) Six sets of values for N and I scores 5 marks, five sets scores 4 marks, etc. [5] Incorrect trend –1. Apparatus set up correctly without help from supervisor. Minor help –1, [2] major help –2 Range – [1] To include N = 1 or 2 and N = 11 or 12. Column headings – [1] Each column heading must contain a quantity and a unit where appropriate. Ignore units in the body of the table. There must be some distinguishing mark between the quantity and the unit (solidus is expected, but accept, for example, I (A)) Consistency of presentation of raw readings of I – [1] All raw values of I must be given to the same number of decimal places. Significant figures – [1] S.f. for 1/I must be the same as, or one more than, the s.f. for I. Check each row. Values of 1/I correct – [1] Underline and check the specified value of 1/I. If incorrect, write in the correct value. (c) (i) Graph Axes – [1] 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. Indicate false origin with FO. Scales must be labelled with the quantity that is being plotted. Ignore units. Allow inverted axes but do not allow the wrong graph. Scale markings should be no more than three large squares apart. Plots – [1] All observations must be plotted. Write a ringed total of plotted points. Do not accept 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. (ii) Line of best fit – [1] Judge by the balance of at least 5 trend plots about the candidate’s line. There must be an even distribution of points either side of the line along the whole length. Indicate best line if candidate’s line is not the best line. Line must not be kinked or thicker than 1 mm. Quality – [1] Judge by scatter of all points about a straight line. All plots in the table must be within 10 Ω of a straight line. Do not award if wrong graph or wrong trend.

Page 3 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9702 32 © UCLES 2010 (iii) Gradient – [1] The hypotenuse of the triangle must be at least half the length of the drawn line. Both read-offs must be accurate to half a small square. If incorrect, write in the correct value. Check for ∆y/∆x (i.e. do not allow ∆x/∆y). y-intercept – [1] Either from graph or by substitution of correct read-offs into y = mx + c. Check for and label false origin. (d) G = gradient value and H = intercept value. [1] Do not credit if a substitution method is used. Range of values (–70Ω Y H Y –30 Ω and 3.5 V Y G Y 5.5 V) with appropriate units. [1] Do not credit if a substitution method is used. [Total: 20] 2 (b) (i) Value of maximum force to 1 d.p. in raw data and greater than 0 N. [1] Evidence of repeated measurements of F in (b)(i) or (d). [1] (ii) Reaches maximum force suddenly (short time); no notice given when releases. [1] (iii) Percentage uncertainty in maximum force. [1] 0.1N Y ∆F Y 0.4 N. If repeated readings have been done then the uncertainty could be half the range. Correct ratio idea required (e.g. 0.2 / F × 100%). (c) (i) Measurement of raw t to the nearest 0.01 mm. [1] (ii) Take repeats in different places / (account for) zero errors. [1] (iii) Maximum force with three slides. Unit required. [1] (d) Measurement of thickness of one slide. [1] Measurement of maximum force with one slide. [1] Quality: F(b)(i) > F(d) > F(c)(iii) [1] (e) Calculation of two values of k. [1] Valid conclusion based on the calculated values of k. [1] Candidates must test against a specified criterion.

Page 4 Mark Scheme: Teachers’ version Syllabus Paper GCE AS/A LEVEL – May/June 2010 9702 32 © UCLES 2010 (f)(i),(ii) Identify limitations and improvements Limitations (4) Improvements (4) Do not credit A Two readings are not enough (to support conclusion Take more (sets of) readings and plot a graph Repeat readings. B Maximum force reached without warning (if not already credited in (b)(ii)) Bs Practical method of recording maximum value e.g. video with playback in slow motion / max-min newton metre / force sensor with data logger / masses with pulley. Parallax error. Solution for parallax error. ‘Use of computer’ to measure maximum force. C t changes due to compression force of magnets / slide thickness non uniform (if not already credited) / thread thickness adds to separation. Method of attaching newton meter without thread / measure and add thread thickness. D Zero error on newton meter when used horizontally. Adjust zero / practical vertical arrangement. Condition of newton meter. E Glass may affect magnetic force / effect of surrounding magnetic materials (e.g. G clamp). Use a variety of materials to separate magnets and test if material affects results / use a non magnetic clamp / glue first magnet to bench. Reference to Earth’s field. F Friction with bench. Method of reducing friction. G Difficulties with alignment of force with magnets. Method of raising magnets / longer loop. X Difficult to measure force due to weak magnets / small force (if validated by SR) More sensitive newton meter. [Total: 20]