Cambridge A Level Physics 9702 — 2023 May/June Paper 3 · Variant 5

1 In this experiment, you will investigate an electrical circuit. You have been provided with a metre rule with a wire attached. (a) ● Set up the circuit shown in Fig. 1.1. 1.5 V d.c. A Y metre rule wire G F w Fig. 1.1 ● F and G are crocodile clips. The distance between F and G is w. Attach G to the wire so that w is approximately 70 cm. ● Close the switch. ● Record the value of w and the ammeter reading I1. w = ............................................................... I1 = ............................................................... ● Open the switch. [1] (b) ● Keep F and G in the same positions so that the value of w remains the same. ● Change some of the connecting leads to set up the circuit shown in Fig. 1.2. A Y G F w Fig. 1.2 ● Close the switch. ● Record the ammeter reading I2. I2 = ............................................................... ● Open the switch. ● Calculate I1I2. I1I2 = ............................................................... [1] (c) Using values of w greater than 55 cm, change w by placing G at different positions on the wire and record I1 and I2. Repeat until you have six sets of readings of w, I1 and I2. Include your values from (a) and (b). 1 Record your results in a table. Include values of I1I2 and w in your table. [10] 1 (d) (i) Plot a graph of I1I2 on the y-axis against w on the x-axis. [3] (ii) Draw the straight line of best fit. [1] (iii) Determine the gradient and y-intercept of this line. gradient = ............................................................... y-intercept = ............................................................... [2] (e) It is suggested that the quantities I1, I2 and w are related by the equation P I1I2 = w + Q where P and Q are constants. Using your answers in (d)(iii), determine values for P and Q. Give appropriate units. P = ............................................................... Q = ............................................................... [2] [Total: 20] You may not need to use all of the materials provided.

Mark scheme: 1(a) 1 1(b) Value of I2 and I2  I1. 1 1(c) Six sets of readings of w (different values), I1 and I2 with correct trend (as w increases I1 and I2 decrease) and without help from the Supervisor scores 5 marks, four sets scores 4 marks etc. 5 Range: wmin ⩽ 60.0 cm and wmax ⩾ 90.0 cm. 1 Column headings: Each column heading must contain a quantity and a unit where appropriate. The presentation of quantity and unit conforms to accepted scientific convention e.g. I1I2/ mA2 and 1 / w / cm–1. 1 Consistency: All values of w must be given to the nearest millimetre. 1 Calculation: Correct calculation of I1I2. 1 Significant figures: Values of I1I2 must be given to the same number of s.f. as (or one more than) the least number of significant figures in I1 or I2. 1 Question Answer Marks 1(d)(i) Axes: Axes must be labelled with the correct quantities. Scales must be chosen so that the plotted points occupy at least half the graph grid in both x and y directions. Scale markings are no more than 2 cm apart (one large square). Sensible scales must be used. Scale must not be awkward (e.g. 3:10 or fractions). 1 Plotting of points: All observations in the table must be plotted on the grid. Diameter of plotted points must be less than half a small square. Points must be plotted to an accuracy of half a small square in both x and y directions. 1 Quality: Trend of points must be positive. All points in the table must be plotted on the grid. It must be possible to draw a straight line that is within  0.05 m–1 (to scale) on the 1 / w axis of all plotted points. 1 1(d)(ii) Line of best fit: ‘Best fit’ is judged by balance of all points on the grid (at least 5 points) about the candidate’s line. There must be an even distribution of points either side of the line along the full length. Lines must not be kinked or thicker than half a small square. Some candidates may choose to identify an anomalous point. If they identify one point as anomalous (e.g. by circling or labelling) then this point is to be disregarded when judging the line of best fit. There must be at least 5 points left after the anomalous point is disregarded. 1 1(d)(iii) Gradient: The hypotenuse of the triangle used should be greater than half the length of the drawn line. Both read-offs must be accurate to half a small square in both x and y directions. The method of calculation must be correct, not x / y. The gradient sign on the answer line must be consistent with the graph drawn. 1 y-intercept: Intercept read directly from the graph, with read-off at 1 / w = 0, accurate to half a small square in y direction. or Correct read-off from a point on the line and substituted correctly into y = mx + c or an equivalent expression. Read-off is accurate to half a small square in both x and y directions. 1 Question Answer Marks 1(e) Value of P = candidate’s gradient and value of Q = candidate’s intercept. Values must not be written as fractions or given to only one significant figure. 1 Units for P consistent with readings: mA2 cm, mA2 m, A2 cm or A2 m and units for Q: mA2 or A2. 1

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2 In this experiment, you will investigate the oscillations of a pendulum. You have been provided with two cylinders A and B. (a) (i) The diameter of cylinder A is D, as shown in Fig. 2.1. cylinder A D Fig. 2.1 Measure and record D. D = ......................................................... [1] (ii) Estimate the percentage uncertainty in your value of D. Show your working. percentage uncertainty = ..................................................... % [1] (b) ● Set up the pendulum as shown in Fig. 2.2. string clamp split cork boss stand L bob bench Fig. 2.2 ● The distance between the bottom of the split cork and the centre of the bob is L. Adjust the position of the string in the split cork until the value of L is approximately 50 cm. ● Measure and record L. L = ............................................................... ● Move the bob through a short distance. ● Release the bob. The bob will oscillate. ● Determine the period T1 of the oscillations of the bob. T1 = ............................................................... [2] (c) (i) ● Use adhesive putty to attach the string to cylinder A as shown in Fig. 2.3. L adhesive putty C string bob cylinder Fig. 2.3 ● C is the point at which the string is attached to the cylinder. Adjust the position of the adhesive putty until the distance between C and the centre of the bob is equal to your value of L from (b). ● Set up the apparatus as shown in Fig. 2.4. cylinder boss CC clamp stand bench Fig. 2.4

Mark scheme: 2(a)(i) Value of (raw) D to the nearest mm and (final) value in the range 6.5–7.5 cm with unit. 1 2(a)(ii) Percentage uncertainty in D based on absolute uncertainty in the range 2–5 mm. Correct method of calculation to find percentage uncertainty (e.g. absolute uncertainty / value from (a)(i))  100). If repeated readings have been taken, then the uncertainty can be half the range (but not zero) provided the working is clearly shown. 1 2(b) Value of T1 in the range 1.21.6 s with unit. 1 Repeats: at least two measurements of nT where n ⩾ 5. 1 2(c)(i) Value of T2 and T2  T1. 1 2(c)(ii) Correct calculation of (T1 ─ T2). 1 2(d) Second values of L and D. 1 Second values of T1 and T2. 1 Second value of (T1 ─ T2)  first value of (T1 ─ T2). 1 2(e)(i) Two values of k calculated correctly. The final k values must not be written as fractions or given to only one significant figure. 1 2(e)(ii) Justification for significant figures in k linked to significant figures in (T1 ─ T2), D and L. 1 2(f) Calculation of percentage difference between candidate’s two k values. Comparison of percentage difference with 10% leading to a consistent conclusion. 1 Question Answer Marks 2(g)(i) A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”). B Difficult to measure D with reason e.g. parallax/shape of jar. C Difficult to set or measure L with reason e.g. locating centre of bob/parallax/bob moves when touched by rule/rule moves/rule not vertical/string slipping through cork. D Large percentage uncertainty in (T1 ─ T2) or large uncertainty in (T1 ─ T2) because T1 and T2 are similar or change in (T1 ─ T2) is small. E Difficult to measure nT with reason e.g. judge start/end of oscillation/complete oscillation. F Difficulty with practical setup e.g. clamping cylinder in right position/ensuring adhesive putty is at the top. 1 mark for each point up to a maximum of 4. 4 2(g)(ii) A Take more readings (for different values of x) and plot a graph or take more readings and compare k values (not “repeat readings” on its own). B Improved method to measure D e.g. use (vernier) calipers/place blocks either side of cylinder. C Improved method to measure L e.g. rule with pointers/clamp rule/measure diameter of bob and add/subtract/find radius. D Use larger values of D/larger difference in D. E Method to improve timing e.g. video/record/film with timer/frame-by-frame/use fiducial marker at the centre of oscillation. F Method to improve setup e.g. use a plumb-line. 1 mark for each point up to a maximum of 4. 4

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