Physics 9702/36 October/November 2023: question paper and mark scheme

Mark scheme

1(a) Value for R in range 0.68–4.7 kΩ with unit. 1 Value for V in range 2.30–3.50 V with unit. 1 1(b) Six sets of readings of R and V with correct trend (as V increases as R increases) and without help from the Supervisor 5 scores 5 marks, five sets scores 4 marks, etc. Range: Rmin = 0.68 kΩ and Rmax = 4.7 kΩ. 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. 1 / R (kΩ–1). Consistency: 1 Values of V must all be given to the nearest 0.01 V. Significant figures: 1 Values of 1 / R should be given to the same number of s.f. as, or one more than, the number of s.f. in the corresponding value of R. Calculation: Values of 1 / R calculated correctly. 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 must be negative. All points in the table (at least 5) must be plotted. It must be possible to draw a straight line that is within ± 0.01 V on the V 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 Δx / Δy. The gradient sign on the answer line must be consistent with the graph drawn. y-intercept: 1 Intercept read directly from the graph, with read-off at 1 / R = 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 accurate to half a small square in both x and y directions. 1(d) Value of a = candidate’s gradient and value of b = candidate’s y-intercept. 1 The values must not be written as fractions or given to only one significant figure. Units for a (e.g. kΩ V) and b (e.g. V) are correct. 1

Mark scheme

2(a) Value for l0 in range 30.0–50.0 cm. 1 2(b) Value(s) for d to nearest mm. 1 Final d in range 1.0–3.0 cm. 1 2(c)(i) Value for h. 1 2(c)(ii) Percentage uncertainty in h based on an absolute uncertainty in the range 0.3–0.5 cm. 1 Correct method of calculation to obtain percentage uncertainty, e.g. (absolute uncertainty × 100 / final value from (c)(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)(iii) Value for lmax to nearest mm and greater than l0. 1 2(d) Second values of d0 and d. 1 Second values of l0, h and lmax. 1 Second value of h less than first value of h. 1 2(e)(i) Two values of C calculated correctly. 1 The final C values must not be written as fractions of given to only one significant figure. 2(e)(ii) Justification for significant figures in C based on the significant figures in (lmax – l0), h and (d0 – d). 1 2(f) Calculation of percentage difference between candidate’s two C values. 1 Comparison of percentage difference with 15% leading to a consistent conclusion. 2(g)(i) A Two readings are not enough to draw a (valid) conclusion (not “not enough for accurate results”, “few readings”). 4 B Difficult to measure l 0 with a reason e.g. hard to get the string straight / hard not to stretch the string. C Difficult to measure d with a reason e.g. parallax or 100 g mass falls off or rule moves string. D Hard to judge if the mass just touches the pad or difficult to align mass with clip before release. E Parallax error when measuring h. F Difficult to measure lmax with a reason e.g. rule unsteady or string may not be vertical. 1 mark for each point up to a maximum of 4. 2(g)(ii) A Take more readings and plot a graph or take more readings and compare C values (not “repeat readings” on its own). 4 B Improved method to find l0 e.g. method to fix one end (e.g. tape to the bench). C Use smaller 100 g mass or mirror scale behind 50 g mass. D Improved method for judging contact e.g. video and replay frame by frame or use pressure pad or use sand tray or place microphone near paper and display trace on CRO. E Clamp rule and use pointer (for h or d). F Measure to bottom of mass (or to paper pad) and subtract diameter of mass (for lmax). 1 mark for each point up to a maximum of 4.