Cambridge A Level Physics 9702 — 2013 Oct/Nov Paper 3 · Variant 6

1 In this experiment, you will investigate the potential difference between two points in a circuit. Use (a) Assemble the circuit of Fig. 1.1. d.c. power supply V zero end of rule tape metre rule zero end crocodile wire of rule clip Fig. 1.1 (b) (i) Connect the voltmeter across the power supply. Record the voltmeter reading E. E = ................................................. [1] (ii) Disconnect the voltmeter from the power supply. (c) (i) Position the voltmeter leads on the wires at distance x from the zero ends of both For rules as shown in Fig. 1.2, where x is approximately 20 cm. Examiner’s Use V x x Fig. 1.2 (ii) Record x and record the voltmeter reading V. Include the sign (+ or −) of V. x = ...................................................... V = ...................................................... (iii) By moving both contacts, change x until the voltmeter reads zero. Record x. x = ................................................. [1] (d) Repeat (c)(i) and (c)(ii) with different values of x until you have six sets of values of x For and V. Examiner’s V Use Include values of in your table. E [10] V (e) (i) Plot a graph of on the y-axis against x on the x-axis. [3] E (ii) Draw the straight line of best fit. [1] (iii) Determine the gradient and y-intercept of this line. gradient = ...................................................... y-intercept = ...................................................... [2] For Examiner’s Use (f) The quantities V, E and x are related by the equation For Examiner’s V Use = ax + b E where a and b are constants. Use your answers from (e)(iii) to determine the values of a and b. Give appropriate units. a = ....................................................... b = ....................................................... [2] You may not need to use all of the materials provided. For Examiner’s

Mark scheme: 1 (b) (i) Value for E in range 2.00 to 3.50 V, with unit. [1] (c) (iii) Value of x (for V = 0) with consistent unit, in range 0.250 to 0.400 m. [1] (d) Six sets of readings of x and V scores 5 marks, five sets scores 4 marks etc. [5] Incorrect trend –1. Help from Supervisor –1. Range: [1] Range of values to include xmin ≤ 20.0 cm and xmax ≥ 80.0 cm. Column headings: [1] Each column heading must contain a quantity and a unit where appropriate. The unit must conform to accepted scientific convention, e.g. V / V or V (V). Consistency: [1] All values of x must be given to the nearest mm. Significant figures: [1] Every value of V/E must be given to the same number of s.f. (or one more than) the least s.f. in the corresponding values of V and E. Calculated values: [1] V/E calculated correctly, including sign. (e) (i) Axes: [1] Sensible scales must be used, no awkward scales (e.g. 3:10). Scales must be chosen so that the plotted points occupy at least half the graph grid in both x and y directions. Scales must be labelled with the quantity that is being plotted. Scale markings should be no more than three large squares apart. Plotting of points: [1] All observations must be plotted. Diameter of plotted points must be ≤ half a small square (“no blobs”). Plots must be accurate to half a small square. Quality: [1] All points in the table must be plotted on the grid for this mark to be awarded. All points must be within 2 cm (to scale) on the x-axis of a straight line. (ii) Line of best fit: [1] Judge by balance of all points on the grid about the candidate’s line (at least 5 points). There must be an even distribution of points either side of the line along the full length. Allow one anomalous point only if clearly indicated by the candidate. Line must not be kinked or thicker than half a small square. GCE AS/A LEVEL – October/November 2013 9702 36 (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 in both the x and y directions. The method of calculation must be correct. y-intercept: [1] Either: Correct read-off from a point on the line is substituted into y = mx + c. Read-off must be accurate to half a small square in both x and y directions. Or: Correct read-off of the intercept directly from the graph. (f) Value of a = candidate’s gradient and value of b = candidate’s intercept. b  in range 0.25 to 0.75. [1] A value presented as a fraction is not allowed. Unit for a correct (e.g. cm–1) and consistent with value, and no unit given for b. [1] [Total: 20]

More questions on Potential difference and power

2 In this experiment, you will investigate the transfer of energy in a collision between rolling Use spheres. (a) You are provided with three spheres as shown in Fig. 2.1. A B B Fig. 2.1 (i) Measure and record the mass mA of the sphere labelled A. mA = ...............................................g [1] (ii) Measure and record the mass mB of the smaller of the two spheres labelled B. mB = ....................................................g (iii) Calculate the value of R, where 2 2mA R = . mA + mB R = ................................................. [1] (iv) Justify the number of significant figures you have given for your value of R. .................................................................................................................................. .................................................................................................................................. ..............................................................................................................................[1] (b) You are provided with a track mounted on a board. Place the smaller sphere B on the track at the lowest point. Measure and record the height h0 of the bottom of the sphere above the bench, as shown in Fig. 2.2. h0 = ................................................. [1] sphere B tape board track h0 bench Fig. 2.2 (c) Place sphere A on the track and resting against the tape, then release it so that it For collides with sphere B. Examiner’s Take measurements to find the maximum height hB reached by sphere B after the Use collision, as shown in Fig. 2.3. hB = ................................................. [2] hB bench Fig. 2.3 (d) Estimate the percentage uncertainty in your value of hB. percentage uncertainty = ................................................. [1] (e) Copy the value of mA from (a)(i). Repeat steps (a)(ii), (a)(iii) and (c) using sphere A and the larger of the two spheres labelled B. mA = ....................................................g mB = ....................................................g R = ...................................................... hB = ...................................................... [3] (f) It is suggested that the relationship between hB and R is For Examiner’s hB – h0 = kR Use where k is a constant. (i) Using your data, calculate two values of k. first value of k = ...................................................... second value of k = ...................................................... [1] (ii) Explain whether your results support the suggested relationship. .................................................................................................................................. .................................................................................................................................. .................................................................................................................................. ............................................................................................................................. [1]

Mark scheme: 2 (a) (i) Value for mA in range 5.0 to 30.0 g. [1] (iii) Correct calculation of R. [1] (iv) Justification for s.f. in R linked to s.f. in mA and (mA + mB ). [1] (b) Value for h0, with unit, to nearest mm. [1] (c) Value for hB >h0. [1] Evidence of repeat readings for hB. [1] (d) Percentage uncertainty in hB based on absolute uncertainty of 2 to 5 mm (or half the range provided this is not zero), and correct method of calculation. [1] (e) Second value of mB. [1] Second value of hB. [1] Quality: hB smaller for larger mB. [1] (f) (i) Two values of k calculated correctly. [1] (ii) Sensible comment relating to the calculated values of k, testing against a criterion specified by the candidate. [1] GCE AS/A LEVEL – October/November 2013 9702 36 (g) (i) Limitations (4 max) (ii) Improvements (4 max) Do not credit A Two readings are not enough Take more readings and plot ‘few readings’/‘take more (to draw a conclusion) a graph/take more readings readings and calculate and calculate more k values average’/ ‘only one reading’/ and compare ‘repeat readings’ on its own B Difficult to judge highest point/ Method of improved ‘too fast’/ hB with reason (e.g. short time measurement of hB (e.g. ball travelling too quick/high at highest point/doesn’t stay video with scale/multiflash speed camera/ slow motion still for long at highest point) photography with scale/use camera/light gates marker/use pointer/trial and error method/mark track with scale/put scale on board behind/ink or chalk on ball/ motion sensors at top of track) C Error when measuring Detailed explanation of ‘set squares’ on own/‘view height(s) because of: parallax/ reducing error perpendicular’/‘parallax error’ ruler not vertical/ruler not on own perpendicular to bench D Bottom of ball not visible Method of improved measurement of height(s) (e.g. measure to top of ball) E Energy lost (e.g. as friction Lubricate track with track or air/sound/hitting sides/not hitting square on) F Difficult to release marble Detail of a mechanical Friction on track without applying a force/ release method (e.g. card difficult not to apply gate) (sideways) velocity Do not allow ‘repeated readings’ or ‘use a computer to improve the experiment’ [Total: 20]

More questions on Physical quantities