RVHS_H2_Physics_P4_Soln

Mark Scheme Question Answer Marks 1(a)(i) current recorded to correct 1 d.p. in mA (setting of digital ammeter) 1 (ii) 1 I recorded in the same s.f. as recorded in the corresponding I. 1 (iii) percentage uncertainty calculated correctly using appropriate method and given to 1 or 2 s.f. E.g. I = 70.4 mA, 1 𝐼 = 14.2 A-1 Using Δ(1 𝐼) 1/𝐼 = Δ𝐼 𝐼 , so percentage uncertainty = ±2 70.4 × 100% = ±2.8% 𝑜𝑟 ± 𝟑% Alternative or max 1 𝐼 = 1 68.4 = 14.6 A-1 taking difference with 1 𝐼 = 14.2 A-1 So absolute uncertainty can be estimated as ±0.4 A-1, so percentage uncertainty = ±0.4 𝟏𝟒.𝟐 × 100% = ±2.8% 𝑜𝑟 ± 𝟑% M1 A1 (b) gradient = 𝑅 𝐸 intercept = 𝑟 𝐸 1 (c)(i) correctly plotting of points with acceptable best fit line drawn 1 (ii) correct method to calculate gradient 1 correct method to calculate intercept 1 (iii) 𝑅 𝑟 obtained by 𝑔𝑟𝑎𝑑𝑖𝑒𝑛𝑡 𝑖𝑛𝑡𝑒𝑟𝑐𝑒𝑝𝑡 1 (iv) line parallel to original line and shifted upwards (or to the left) 1

Question Answer Marks 2(a) • L = 98.5 ± 0.1 cm 1 (b) • y2 lesser than y1 • y, y2 and y1 are all recorded to the nearest 0.1 cm • Repeated measurements 1 (c) Tabulation • Collected 5 sets of data for m, y1 and y2. • Correct trend (0 marks for 4 sets and fewer) 1 Column Heading • Each column heading must contain a quantity and a unit: y/cm, m/g • No split table 1 Raw data (i.e x and I): Precision of recording • All values of y1 and y2. to nearest mm & • All values of m to nearest g 1 Calculated quantity: Accuracy of calculation All values of y calculated correctly with the correct d.p 1 (d) Graph: Scale, Size & Axes • Sensible scales, no awkward scales (eg 3 units into 10 small squares) • Plotted pts occupy at least ½ the graph grid in both x & y directions • Axes labelled with the quantity & unit {ECF for wrong units in (c)} Successive scale markings: no more than 20 small squares apart. 1 Plotting of Points • ALL observations in table must be plotted • accurate to within half a small square. • Thickness of plots (ie the crosses, ‘x’)  half a small square 1 Best fit line & Anomaly • Minimum number of 4 non-anomalous points. • Line drawn with approx. equal number of points on either side of line (anomalous points not considered). • Line not be kinked/disjointed or thicker than half a small square • Anomalous plot clearly indicated (eg by a circle or labelled.) • Allow 1 anomalous plot only. 1

• {Rule of thumb: A plot is considered anomalous if it is > 4 mm from line of best fit.} Determination of Gradient  Recorded the 4 coordinates for gradient calculation correctly  Hypotenuse of triangle > half length of line drawn  No obscurity of the 2 points used for gradient calculation. {Hence triangle must not be drawn too near a data plot.} 1 Determination of y-intercept Vertical intercept calculated using a point on the line {not from the table} & value of gradi