Cambridge A Level Physics 9702 — 2007 May/June Paper 3 · Variant 2

This document consists of 8 printed pages and 4 blank pages. SPA (SLM/CG) T26891/3 © 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 ON ANY BARCODES. Answer all 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. * 5 0 1 9 0 0 8 1 2 9 * PHYSICS 9702/32 Paper 32 Advanced Practical Skills 2 May/June 2007 2 hours Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. For Examiner’s Use 1 2 Total

3 9702/32/M/J/07 [Turn over 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 current I through a resistor R3 as its resistance is changed. (a) (i) Use the voltmeter to measure the e.m.f. E of the power supply. E = … V (ii) Connect the circuit shown in Fig. 1.1. R1 and R2 are labelled, and R3 may be chosen from any one of the remaining resistors. Each resistor carries a label indicating its resistance. E R1 R2 R3 I A Fig. 1.1 (iii) Record the values of the current I and the resistance R3 of resistor R3. I = … A R3 = …Ω

4 9702/32/M/J/07 For Examiner’s Use © UCLES 2007 (b) Change the resistor R3 and repeat (a)(iii) until you have six sets of readings for I and R3. Include values of 1 I in your table of results. (c) (i) Plot a graph of 1 I (y-axis) against R3 (x-axis). (ii) Draw the line of best fit. (iii) Determine the gradient and the y-intercept of the graph. gradient = … y-intercept = …

5 9702/32/M/J/07 [Turn over For Examiner’s Use © UCLES 2007

6 9702/32/M/J/07 For Examiner’s Use © UCLES 2007 (d) The relationship between I and R3 is 1 I =
R1 + R2 ER2 R3 + R1 E where R1 is the resistance of the resistor R1, R2 is the resistance of the resistor R2, and E is the e.m.f. of the power supply. Using your answers from (a)(i) and (c)(iii), determine values of R1 and R2. R1 = … R2 = …

8 9702/32/M/J/07 For Examiner’s Use © UCLES 2007 You may not need to use all of the materials provided. 2 In this experiment you will investigate how the rebound height h of a table-tennis ball is related to the height d from which it is dropped. If air resistance is ignored, then theory predicts that e = h d where e is a constant. Air resistance may be ignored if d < 40 cm. (a) (i) Mount a half-metre rule vertically using a stand, boss and clamp. (ii) Place the table-tennis ball next to the rule and record d. Release the ball and make measurements to determine the rebound height h, as shown in Fig. 2.1. h d Fig. 2.1 d = … h = … (iii) Explain how you used the apparatus to ensure that the rebound height h was measured as accurately as possible. … … … …

9 9702/32/M/J/07 [Turn over For Examiner’s Use © UCLES 2007 (iv) Estimate the percentage uncertainty in h. percentage uncertainty in h = … (v) Calculate a value for e. e = … (b) Repeat (a)(ii) and (b)(v) using a different value of d. d = … h = … e = … (c) Do the results of your experiment indicate that e is a constant within the limits of experimental accuracy? Explain your reasoning clearly. … … … …

10 9702/32/M/J/07 For Examiner’s Use © UCLES 2007 (d) (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 9702/32/M/J/07 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. BLANK PAGE

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Subsidiary Level and GCE Advanced Level MARK SCHEME for the May/June 2007 question paper 9702 PHYSICS 9702/32 Paper 32 (Advanced Practical Skills 2), 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 May/June 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 – May/June 2007 9702 32 © UCLES 2007 1 Manipulation, measurement and observation Successful collection of data (a) (i) Measurement of e.m.f. of power supply [1] (b) Measurements [5] Five marks for six sets of readings for I and R3, four for five sets, etc. (b) Circuit set up without help from Supervisor [1] Range and distribution of values (b) R3 = 33 or 47Ω and R3 = 560 or 680Ω must be included [1] Quality of data (Graph) Judge by scatter of points about the best fit line. Trend must be correct. [1] At least 5 plots are needed for this mark to be scored. Presentation of data and observations Table: layout (b) 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 (i.e. solidus is expected, but accept, for example, I (A)). Table: raw data (b) Consistency of presentation of raw readings [1] All values of I must be given to the same number of decimal places. Table: calculated quantities (b) Significant figures [1] Apply to 1/I only. If I is given to 2 sf, then accept 1/ I to 2 or 3 sf. If I is given to 3 sf, then accept 1/ I to 3 or 4 sf. If I is given to 4 sf, then accept 1/ I to 4 or 5 sf. (b)Values of 1/ I correct. [1] Check a value. If incorrect, write in the correct value.

Page 3 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2007 9702 32 © UCLES 2007 Graph: layout (Graph) Axes [1] Sensible scales must be used. Awkward scales (e.g. 3:10) are not allowed. There should not be more than three large squares between axis labels. Scales must be chosen so that the plotted points must occupy at least half the graph grid in both x and y directions. Scales must be labelled with the quantity which is being plotted. Ignore units. Do not penalise reversed axes or if the wrong graph has been plotted. Graph: plotting of points (Graph) All observations must be plotted. [1] Ring and check a suspect plot. Tick if correct. Re-plot if incorrect (and re-check quality mark). Work to an accuracy of half a small square. Graph: trend line (Graph) Line of best fit (must be 5 or more plots) [1] 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. Analysis, conclusions and evaluation Interpretation of graph (c) (iii) Gradient [1] The hypotenuse must be 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). (c) (iii) y-intercept [1] The value must be read to the nearest half square. The value can be calculated using ratios or y = mx + c. If a false origin has been used then label FO. Drawing conclusions (d) Must be in range 40.0 to 55.0 Ω. [1] Value for R1 obtained from y-intercept x E. 2 or 3 sf. Unit required (d) Value for R2 [1] Should be 220 Ω ± 50 Ω unless Supervisor has used different resistors to those specified. Method of working must be correct. 2 or 3 sf. Unit required. [Total for Question 1: 20]

Page 4 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2007 9702 32 © UCLES 2007 2 Manipulation, measurement and observation Successful collection of data (a) (ii) First value of d (less than 40 cm) no more precise than 1 mm. [1] (a) (ii) First value of h (less than d) [1] (a) (iii) Method of measuring h accurately [1] e.g. Use of set squares to indicate height / repeat to refine position. Do not accept repeated readings for this mark Do not accept just ‘use a set square’ (b) Second value of d (less than 40 cm) [1] (b) Second value of h (less than d) [1] (b) Evidence of repeated measurements for h (first or second reading) [1] Quality of data (b) Values of e within 10% of each other [1] Presentation of data and observations Display of calculation and reasoning (b) Values of e calculated correctly [2] One mark each Calculations must be checked (c) Consideration of the percentage uncertainty in h from (a)(iv) is expected. [1] Knowledge of error propagation methods is not required.

Page 5 Mark Scheme Syllabus Paper GCE A/AS LEVEL – May/June 2007 9702 32 © UCLES 2007 Analysis, conclusions and evaluation Drawing conclusions (c) Conclusion [1] Sensible comments relating to values of e. Incorrect ideas score zero. Estimating uncertainties (a) (iv) Percentage uncertainty in h [1] If repeated readings have been done then the uncertainty must be half the range. Absolute uncertainty must be 2 to 10 mm. Correct ratio idea required. Identifying limitations (d) (i) Relevant points must be underlined and ticked. [4] Some of these might be: A Two sets of readings not enough (to draw valid conclusion) B Hard to judge rebound height, with reason C Parallax (error in measuring h) D Difficult to release without applying a force E Rule may not be vertical / perpendicular F Only cm divisions on rule (if borne out by readings) G Inconsistent bounce Suggesting improvements (d) (ii) Relevant points must be underlined and ticked. [4] Some of these might be: A Take several d values and plot graph/compare e values B Use video and play back slowly/position sensor C Method of reducing parallax problem (adjustable marker/drop many times to refine value of h/assistant to drop ball/ensure measurement taken at eye level) D Mechanical method of release/hold ball against stop E Method of making rule vertical G Use flat surface/turn off fans Do not allow ‘repeated readings’ (unless qualified by ‘plot a graph’) Do not allow ‘use a computer to improve the experiment’ Do not allow ‘increase d’ [Total for Question 2: 20]