Cambridge A Level Physics 9702 — 2018 May/June Paper 3 · Variant 4

1 In this experiment, you will investigate an electrical circuit. You are provided with groups of components connected in parallel. The circuit symbol for each of these components is shown in Fig. 1.1. + Fig. 1.1 (a) • Assemble the circuit shown in Fig. 1.2. S component holders movable A lead L + + 3 V d.c. C + + V B 5 components in parallel Fig. 1.2 • Check that the positive terminals of the power supply, component C and the groups of components are connected as shown in Fig. 1.2. • Connect the movable lead L to terminal A. • Close the switch S. • Record the voltage VS shown on the voltmeter. VS = ............................................................... • Open switch S. [1] (b) • Record the total number n of components in parallel in the component holders. n = ............................................................... • Move the movable lead L and connect it to terminal B. • Close switch S. • Open switch S after approximately 5 s. • Move the movable lead L and connect it to terminal A. Immediately record the voltage V shown on the voltmeter. V = ...........................................................[2] (c) Change n and repeat (b) until you have six sets of values of n and V. One of the component holders may be left empty if required. 1 Record your results in a table. Include your values from (b). Also include values of in your V table. [9] 1(d) (i) Plot a graph of on the y-axis against n on the x-axis. [3] V (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 V and n are related by the equation 1 = an + b V where a and b are constants. Use your answers in (d)(iii) to determine the values of a and b. Give appropriate units. a = ............................................................... b = ............................................................... [2] [Total: 20] You may not need to use all of the materials provided.

Mark scheme: 1(a) Value of VS in range 2.00–4.00 V, with unit. 1 1(b) Value of V less than VS. 1 Evidence of repeat readings of V. 1 1(c) Six sets of readings of n and V with the correct trend and without help from the Supervisor scores 4 marks, five sets scores 3 marks, etc. 4 Range: nmin = 1 or 0 and nmax ⩾ 7. 1 Column headings: Each column heading must contain a quantity and a unit where appropriate. The presentation of quantity and unit must conform to accepted scientific convention, e.g. (1 / V) / V–1 or 1/V (V–1). 1 Consistency: All raw values of V must be given to 0.01 V, without trailing zeros. 1 Significant figures: Significant figures for every value of 1 / V the same as, or one greater than, the s.f. of V as recorded in the table. 1 Calculation: Values of 1 / V calculated correctly. 1 1(d)(i) Axes: Sensible scales must be used, no awkward scales (e.g. 3:10 or fractions). 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. 1 Plotting of points: All observations in the table must be plotted on the grid. Diameter of plotted points must be ⩽ half a small square (no “blobs”). Points must be plotted to an accuracy of half a small square in both x and y directions. 1 Quality: All points in the table must be plotted (at least 5) for this mark to be awarded. Scatter of points must be no more than ± 0.025 V–1 from a straight line in the 1 / V direction. 1 Question Answer Marks 1(d)(ii) Line of best fit: Judge by balance of all points on the grid about the candidate’s line. 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. There must be at least 5 points left after the anomalous point is disregarded. Line must not be kinked or thicker than half a small square. 1 1(d)(iii) Gradient: The hypotenuse of the triangle used should be greater than half the length of the drawn line. The method of calculation must be correct. Do not allow ∆x / ∆y. Both read-offs must be accurate to half a small square in both the x and y directions. Sign of gradient must match graph. 1 y-intercept: Correct read-off from a point on the line substituted into y = mx + c or an equivalent expression. Read-off must be accurate to half a small square in both x and y directions. or Intercept read directly from the graph, with read-off at n = 0, accurate to half a small square in the y direction. 1 1(e) Value of a equal to candidate’s gradient and value of b equal to candidate’s intercept. 1 Unit for a is V–1 and unit for b is V–1. 1

More questions on Practical circuits

2 In this experiment, you will investigate the motion of a plastic bottle floating in water. (a) • Pour 500 cm3 of water from the jug into the beaker (1 ml = 1 cm3). • Pour this water into the bottle. • Place the 100 g mass hanger with two 100 g slotted masses in the bottle, as shown in Fig. 2.1. bottle water mass hanger slotted masses Fig. 2.1 • Assume that the density of the added water is 1.0 g cm–3 (1.0 cm3 of water has a mass of 1.0 g). Calculate the total mass M of the mass hanger, slotted masses and water in the bottle. M = ......................................................kg [1] (b) (i) • Carefully place the bottle in the bucket of water so that the bottle floats vertically in the water. • Carefully push the bottle down, ensuring that its top remains above the level of the water in the bucket. • Release the bottle so that it oscillates vertically, as indicated in Fig. 2.2. bucket water bottle water Fig. 2.2 • Take measurements to find the period T of the oscillations. T = ...........................................................[2] (ii) Estimate the percentage uncertainty in your value of T. percentage uncertainty = ...........................................................[1] (c) (i) • Remove the bottle from the bucket and place it in the tray. • Add three more 100 g slotted masses to the mass hanger in the bottle. • Calculate the new total mass M. M = ......................................................kg [1] (ii) Repeat (b)(i). T = ...........................................................[2] (d) It is suggested that the relationship between M and T is M = kT 2 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. ........................................................................................................................................... ...........................................................................................................................................

Mark scheme: 2(a) Correct calculation of M. 1 2(b)(i) Value for T in range 0.50–1.00 s, with unit. 1 Evidence of repeat readings of time, with at least two sets of nT where n ⩾ 5. 1 2(b)(ii) Absolute uncertainty in time measurement of 0.20–0.50 s and correct method of calculation to obtain percentage uncertainty. If repeated readings have been taken, then the absolute uncertainty can be half the range (but not zero) if the working is clearly shown. 1 2(c)(i) Second value of M. 1 2(c)(ii) Second value of T. 1 Quality: T greater for greater M. 1 2(d)(i) Two values of k calculated correctly. 1 2(d)(ii) Valid comment relating to the calculated values of k, testing against a criterion specified by the candidate. 1 2(e)(i) Value(s) for D to nearest mm and value for D (on answer line) in range 0.050–0.200 m. 1 2(e)(ii) Correct calculation of A. 1 2(e)(iii) Correct calculation of ρ using second value of k. 1 Question Answer Marks 2(f)(i) A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”). B Reason for M not being accurate, e.g. mass of bottle ignored/uncertainty in the volume of water linked to precision of beaker. C Difficulty with oscillation with reason, e.g. masses move/bottle hits side of bucket/does not oscillate vertically/other modes of oscillation. D Difficult to measure D with reason, e.g. bottle flexes when measuring D/non-uniform D/bottle not circular/D varies with depth. E Difficult to judge when an oscillation starts/ends/is completed. 1 mark for each point up to a maximum of 4. 4 2(f)(ii) A Take more readings and plot a graph or take more values of k and compare (not “repeat readings” on its own). B Use electronic balance/top-pan balance or use measuring cylinder. C Method of fixing mass hanger in position in bottle, e.g. Blu-Tack, glue, tape or use suitable alternative to slotted masses, e.g. sand/lead shot/single mass or use wider bucket/larger diameter. D Use vernier/digital calipers or details of alternative method to find D, e.g use two set squares/two wooden blocks or measure D in different directions/positions and find average. E Use video and timer/video and view frame by frame or position/motion sensor above bucket. 1 mark for each point up to a maximum of 4. 4

More questions on Simple harmonic oscillations