Cambridge A Level Physics 9702 — 2006 May/June Paper 5 · Variant 1

This document consists of 9 printed pages and 3 blank pages. SPA (SJF3701/CG) T03735/2 © UCLES 2006 [Turn over UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS General Certificate of Education Advanced Level PHYSICS 9702/05 Paper 5 Practical Test May/June 2006 1 hour 30 minutes Candidates answer on the Question Paper. Additional Materials: As listed in the Confidential Instructions. 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. Answer both questions. 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. Marks are mainly given for a clear record of the observations actually made, for their suitability and accuracy, and for the use made of them. 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. Centre Number Candidate Number Name For Examiner’s Use 1 2 Total

3 [Turn over 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use It is recommended that you spend about 60 minutes on this question. You may not need to use all of the materials provided. 1 In this experiment you will investigate how the current in a wire depends on the length of the wire. You will use the results of your experiment to determine a value for the resistivity of the material of the wire. (a) Set up the circuit shown in Fig. 1.1. Use a crocodile clip to attach a connecting lead to the bare wire at the zero end of the metre rule. The crocodile clip should be attached as close as possible to the zero mark on the rule. Fig. 1.1 (b) (i) Adjust the power supply to give an output voltage of 3.0 V. Place the connecting lead P onto the wire near the centre. Measure and record the length x and the current I. x = …………………………………. m I = …………………………………. A (ii) State one way of improving the precision in the measurement of x. … … … … metre rule 100 P 0 x A V

(c) Change the value of x and repeat (b) (i) until you have six sets of readings of length x and current I for values of x in the range 0.400 m < x < 0.900 m. You may need to adjust the setting on the power supply to maintain a constant output potential difference of 3.0 V. Include in your table of results values for lg (x/m) and lg (I/A). (d) (i) Plot a graph of lg (x/m) (y-axis) against lg (I/A) (x-axis). (ii) Draw the line of best fit. (iii) Determine the gradient and the y-intercept of this line. gradient = …………………………………. y-intercept = …………………………………. 4 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use

5 [Turn over 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use

6 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use (e) x and I are related by a simple power law of the form x = kI n where n and k are constants. Use your answers from (d) (iii) to find the values of k and n. You need not be concerned with the units of these quantities. k = …………………………… n = …………………………… (f) A simple theoretical treatment of this circuit gives where V is the potential difference across the wire, A is the cross-sectional area of the wire and ρ is the resistivity of the material of the wire. (i) Remove the crocodile clip from the wire. Use a micrometer screw gauge to measure the diameter of the wire. diameter of wire = ……………………………… mm (ii) Determine the cross-sectional area A of the wire. A = ……………………………… m2 k = VA ρ

(iii) Determine the percentage uncertainty in A. percentage uncertainty in A = ………………………………… % (g) Using your answers from (e) and (f), determine a value for ρ. ρ = …………………………… Ωm (h) The experiment is repeated with a wire of the same material but twice the diameter. Suggest what value of k would be obtained. k = …………………………………….. 7 [Turn over 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use

It is recommended that you spend about 30 minutes on this question. 2 A fine wire mesh has individual wires that are spaced very close together. See Fig. 2.1. Fig. 2.1 The mesh behaves like two diffraction gratings placed at right angles to each other. The diffraction grating formula is d sinθ = nλ. The spacing between the wires of the mesh is to be found accurately. Design a laboratory experiment using light of a single wavelength to determine the spacing between the wires. You may assume that the wavelength of the light is known. You should draw a detailed labelled diagram showing the arrangement of your apparatus. In your account you should pay particular attention to (a) the type of light source to be used, giving a reason for your choice, (b) the procedure to be followed and the measurements that would be taken, (c) how the measurements would be used to find values of θ, (d) how the spacing between the wires would be deduced, (e) any safety precautions you may take. 8 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use

Diagram … … … … … … … … … … … 9 [Turn over 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use

… … … … … … … … … … … … … … … … … … … … … … … … … … … 10 9702/05/M/J/06 © UCLES 2006 For Examiner’s Use

BLANK PAGE 12 9702/05/M/J/06 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 University of Cambridge Local Examinations Syndicate (UCLES), which is itself a department of the University of Cambridge.

UNIVERSITY OF CAMBRIDGE INTERNATIONAL EXAMINATIONS GCE Advanced Level and GCE Advanced Subsidiary Level MARK SCHEME for the May/June 2006 question paper 9702 PHYSICS 9702/05 Paper 5 Maximum mark 30 This mark scheme is published as an aid to teachers and students, to indicate the requirements of the examination. It shows the basis on which Examiners were initially instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners’ meeting before marking began. Any substantial changes to the mark scheme that arose from these discussions will be recorded in the published Report on the Examination. 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. The minimum marks in these components needed for various grades were previously published with these mark schemes, but are now instead included in the Report on the Examination for this session. • CIE will not enter into discussion or correspondence in connection with these mark schemes. CIE is publishing the mark schemes for the May/June 2006 question papers for most IGCSE and GCE Advanced Level and Advanced Subsidiary Level syllabuses and some Ordinary Level syllabuses.

Page 1 Mark Scheme Syllabus Paper GCE A LEVEL – May/June 2006 9702 05 © University of Cambridge International Examinations 2006 1 (b) (ii) Expect to see x read to nearest mm and then: Use connector with sharp edge [1] Position the wire on top of the scale on the rule to reduce parallax error (c) Readings [3] Write the number of readings as a ringed total by the results table. 6 sets of readings scores 1 mark. Check a value for lg(x/m) and a value for lg(IA). Underline checked values. Ignore small rounding errors. Tick if correct; 1 mark each. If incorrect then write in correct value. Excessive alterations in the table then –1. If minor help is given with the circuit, then –1. If excessive help is given then –2. Please indicate when help has been given to a candidate by writing SR at the top of the front page of the candidate's script. Also, please indicate the type of help that has been given by writing a brief comment by the table of results. Column headings. Allow lg(x/m) and lg(I/A). Allow POT errors. [1] There must be some distinguishing mark between the quantity and its unit. Please
or underline each correct column heading to show that it has been seen. Consistency of raw readings in the table of results [1] Apply to x and I only. Expect to see I to either 0.01 A or 0.1 A. Expect to see all the values of x given to the nearest millimetre. Indicate using a vertical line down each column of raw readings to show it has been seen and a
C if correct. (d) (i) Axes [1] Each axis must be labelled with a quantity. Allow lg(x), lgx, lg(x/m) but not lgx/m. Scales must be such that the plotted points occupy more than half the graph grid in both the x and y directions. Do not allow more than 3 large squares between scale markings. Do not allow awkward scales (e.g. 3:10, 6:10, 7:10, etc.). Plotting of points [1] Count the number of plots on the grid and write this value by the line and ring it. Do not allow plots in the margin area. The number of plots must correspond to the number of observations (at least 6). Do not award this mark if the number of plots is less than the number of observations. Check one suspect plot. Circle this plot. Tick if correct. If incorrect then mark the correct position with a small cross and use an arrow to indicate where the plot should have been. Allow errors less than half a small square.

Page 2 Mark Scheme Syllabus Paper GCE A LEVEL – May/June 2006 9702 05 © University of Cambridge International Examinations 2006 (ii) Line of best fit [1] There must be a reasonable balance of points about the line of best fit. If one of the plots is a long way from the trend of the other plots then allow this plot to be ignored when the line is drawn. One mark can be awarded if the line of best fit is ‘reasonable’, but not quite right. (iii) Measurement of gradient [1] The hypotenuse of the triangle must be greater than half the length of the drawn line. If read-offs are inaccurate by half a small square, or more, then zero. Please indicate the vertices of the triangle used by labelling with ∆. One mark for the read-offs. The value must be negative. Value should be around -1.0. ∆x/∆y scores zero. Ignore units. y-intercept. Expect –0.8. Ignore units. [1] Check the read-off. Value must be within half a square. Accept correct substitution from a point on the line into y = mx + c. Allow ecf from (d)(iii) gradient for m. (e) lg x = n lg I + lg k [1] This can be implied from the working. Value for n (from gradient). Allow ecf from (d)(iii) gradient. n = –1.0. Ignore unit. [1] Value for k (from 10y-intercept). Allow ecf from (d)(iii) y-intercept. k = 0.158. Ignore unit. [1] Working must be checked. (f) (i) Value of diameter of wire (± 0.02 mm of SV). (36 swg, diameter = 0.18 mm) [1] (ii) Cross-sectional area correct. (36 swg, Area = 2.5 x 10 –8 m2) [1] (iii) Percentage uncertainty in area [2] One mark for percentage uncertainty in r. One mark for % uncertainty x 2. (g) Correct value of ρ. No POT error allowed. Expect to see ρ = 4.7 x 10–7 Ωm [1] Check the substitution and consistency of units. (h) k = 4 x previous value. Allow ecf (g). Expect to see k = 1.9 x 10–6 Ωm [1] [Total: 20 marks]

Page 3 Mark Scheme Syllabus Paper GCE A LEVEL – May/June 2006 9702 05 © University of Cambridge International Examinations 2006 Question 2 A1 Diagram of arrangement (light source/mesh/screen or collimator/mesh/telescope) [1] A2 Fringes or dots shown on screen. May be shown on diagram. [1] A3 Some sensible discussion of coherence [1] A4 Use of laser or single slit (and lens) in collimator [1] B1 Measurements: distance from mesh to screen and separation between fringes [1] OR measure an angle from the spectrometer table B2 n = 1; find separation between central fringe and first bright fringe [1] OR measure angle between central bright beam and first order beam using scale on table B3 Use of θ λ sin = n to find d. n must be clearly identified [1] C Any safety precaution [1] e.g. use goggles/do not look directly into laser beam/cover over sodium lamp do not touch the bulb D Any good/further detail [2] Examples of creditworthy points might be: Take readings with mesh in different positions to average d Sketch/suggestion of two-dimensional array of dots on screen Laser + mesh + screen all at same height λ = 589 nm for sodium lamp or about λ = 630 nm for He/Ne laser/semiconductor laser D of the order of 1 m to 4 m (laser method) Measure 2θ and divide by two to reduce uncertainty in θ Repeat experiment with 2nd order (3rd order etc.) beams Detail relating to setup/use of spectrometer Allow other valid points. [Total: 10 marks]