Cambridge A Level Physics 9702 — 2023 Oct/Nov Paper 3 · Variant 1

1 In this experiment, you will investigate an electric circuit. You have been provided with a wooden strip with wire attached to nails. (a) ● Set up the circuit shown in Fig. 1.1. wooden strip wire nail F 1.5 V d.c. G H nail N L R I1 A A I2 Fig. 1.1 ● F, G and H are crocodile clips. The distance between nail N and G is L, as shown in Fig. 1.1. Adjust the position of G until L is approximately 40 cm. ● Close the switch. ● Record L and the ammeter readings I1 and I2. L = ............................................................... I1 = ............................................................... I2 = ............................................................... ● Open the switch. [3] (b) Change L by adjusting the position of G between N and H. Measure and record L, I1 and I2. Repeat until you have six sets of values of L, I1 and I2. I2 Record your results in a table. Include values of in your table. (I1 – I2) [9] I2(c) (i) Plot a graph of on the y-axis against L on the x-axis. [3] (I1 – I2) (ii) Draw the straight line of best fit. [1] (iii) Determine the gradient and y-intercept of this line. gradient = ............................................................... y-intercept = ............................................................... [2] (d) It is suggested that the quantities L, I1 and I2 are related by the equation I2 = PL + Q (I1 – I2) where P and Q are constants. Using your answers in (c)(iii), determine the values of P and Q. Give appropriate units. P = ............................................................... Q = ............................................................... [2] [Total: 20] You may not need to use all of the materials provided.

Mark scheme: Question Answer Marks 1(a) Value of final L in the range 38.0–42.0 cm with unit. 1 Values of I1 and I2 each less than 1 A and each with unit. 1 I1 > I2. 1 1(b) Six (or more) sets of readings of L (different values), I1 and I2 with correct trend (as L increases, I1 increases and I2 4 decreases) and without help from the Supervisor scores 4 marks, five sets scores, 3 marks etc. Range: Lmin ⩽ 10.0 cm and Lmax ⩾ 70.0 cm. 1 Column headings: 1 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. L / cm, I1 / mA. I2 / (I1 – I2) must have no unit. Consistency: All values of L must be given to the nearest 0.1 cm. 1 Significant figures: 1 All values of I2 / (I1 – I2) must be given to the same number of s.f. (or one more than) the least number of s.f. in I1, I2 and (I1 – I2) values. Calculation: Values of I2 / (I1 – I2) are correct. 1 1(c)(i) Axes: 1 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 the x and y directions. Scale markings are no more than 2 cm (one large square) apart. Sensible scales must be used. Scales must not be awkward (e.g. 3:10 or fractions). Plotting of points: 1 All observations in the table must be plotted on the grid. Diameter of plotted points must be ⩽ half a small square. Points must be plotted to an accuracy of half a small square in both x and y directions. Quality: 1 Trend of points on graph must be negative. All points in the table must be plotted (at least 5). It must be possible to draw a straight line that is within  5 cm ( 0.05 m) to scale on the L axis of all plotted points. 1(c)(ii) Line of best fit: 1 ‘Best fit’ is judged by the 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 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(c)(iii) Gradient: 1 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 the 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. y-intercept: 1 Intercept read directly from the graph where L = 0 and accurate to half a small square in y direction. or Correct read-off from a point on the line substituted correctly into y = mx + c or an equivalent expression. Read–off accurate to half a small square in both x and y directions. 1(d) Value of P = candidate’s gradient and value of Q = candidate’s y-intercept. 1 Values must not be written as fractions or given to only one significant figure. 1(d) Unit for P correct e.g. cm–1 or m–1 or mm–1 and no unit for Q. 1

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2 In this experiment, you will investigate the displacement of water from a container. (a) (i) The apparatus has been set up as shown in Fig. 2.1. stand string loop attached to ramp trolley clamp boss string over pulley ramp pulley bench Fig. 2.1 ● Ensure that the string passes over the pulley as shown in Fig. 2.1. ● Hang the mass hanger and four slotted masses from the small string loop, as shown in Fig. 2.2. θ small string loop mass hanger and masses floor ≈ 4 cm Fig. 2.2 ● Adjust the apparatus until the bottom of the masses is approximately 4 cm above the floor. ● Place the two containers so that the mass hanger and masses hang inside the smaller container, as shown in Fig. 2.3. larger container floor smaller container Fig. 2.3 ● Pull the trolley up the ramp. Ensure that the string runs over the pulley, and the mass hanger and masses hang above the smaller container. Stop the trolley when its back wheels are approximately 10 cm from the top of the ramp or the small string loop touches the pulley. ● Release the trolley. Ensure that the mass hanger and the masses hang inside the smaller container when the trolley stops. ● Lift the string, mass hanger and masses onto the bench. ● The angle between the ramp and the bench is θ, as shown in Fig. 2.2. Adjust the apparatus until θ is between 10° and 15°. ● Measure and record θ. θ = ....................................................... ° [2] (ii) Calculate cos θ. cos θ = ......................................................... [1] (b) (i) ● Without spilling any water into the larger container, completely fill the smaller container with water, as shown in Fig. 2.4. water Fig. 2.4 ● Hang the mass hanger and masses from the small string loop. Ensure that the string runs over the pulley, and the mass hanger and masses hang above the smaller container. ● Pull the trolley up the ramp. Stop the trolley when its back wheels are approximately 10 cm from the top of the ramp or the small string loop touches the pulley. ● Release the trolley. The masses will fall into the water and water will overflow into the larger container. ● Lift the string, mass hanger and masses onto the bench. ● Measure and record the volume V of water that is now in the larger container. V = ................................................. cm3 [2] (ii) Estimate the percentage uncertainty in your value of V. Show your working. percentage uncertainty = ..................................................... % [1]

Mark scheme: 2(a)(i) Value(s) of to the nearest degree. 1 Final value of in the range 10–15°. 1 2(a)(ii) Correct calculation of cos . 1 2(b)(i) Value(s) of V to the nearest cm3. 1 Evidence of repeat values of V. 1 2(b)(ii) Percentage uncertainty based on an absolute uncertainty in V in range 2–5 cm3. 1 Correct method of calculation to find percentage uncertainty e.g. absolute uncertainty  100 / final V value from (b)(i). If repeated readings have been taken, then the uncertainty can be half the range (but not zero) if the working is shown clearly. 2(c) Second value of . 1 Second value of V. 1 Second value of V is greater than first value of V. 1 2(d)(i) Two values of k calculated correctly. 1 The final k values must not be written as fractions or given to only one significant figure. 2(d)(ii) Justification for significant figures in k linked to significant figures in V and (not cos ). 1 2(e) Calculation of percentage difference between candidate’s two k values. 1 Comparison of percentage difference with 15% leading to a consistent conclusion. 2(f)(i) A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”). 4 B Difficulty filling container with a reason e.g. overflows as filling or restricted access or small container not level or if put a little too much water in it overflows. C Difficulty measuring accurate value of V with a reason e.g. some water stays in large container or water sticks to outside of small container or water splashes out. D Difficulty with setup e.g. holding trolley and positioning masses at the same time. E Difficulty with alignment with reason e.g. container moves as being filled or container may be replaced in a different position after measuring V or masses hit container. F Difficult to ensure the trolley is held at same position each time. 1 mark for each point up to a maximum of 4. 2(f)(ii) A Take more readings (for different values of ) and plot a graph or take more readings and compare k values (not 4 “repeat readings” on its own). B Improved method of filling e.g. pipette/syringe/burette. C Improved method to measure V e.g. measure volume needed to top up smaller container. D Improved method for holding trolley e.g. clamp trolley/stop for trolley. E Detailed method to improve alignment e.g. marked sheet taped on floor. F Improved method of to ensure the same position of release e.g. use of gate/mark ramp/use marker. 1 mark for each point up to a maximum of 4.

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