OCR 2023 GCE Physics B H557/03: Practical skills in physics A Level Question Paper & Mark Scheme (Merged)

2 © OCR 2023 zinc cathode copper anode lemon resistor V Section A 1 A cell can be made by inserting a zinc cathode and a copper anode into a lemon. A high resistance voltmeter is used in the circuit shown in Fig. 1.1 to measure the p.d. across the lemon when different resistors are placed across the cell. Fig. 1.1 (a) Table 1 below shows the data recorded. Table 1 resistance / kΩ potential difference / mV current / μA 3.3 540 164 6.6 666 101 10.0 738 13.3 765 16.6 784 47 20.0 812 41 (i) Calculate the current and complete the missing rows in Table 1. [1] 3 © OCR 2023 Turn over (ii) Plot the missing points on the graph in Fig. 1.2 and draw the line of best fit. [2] Fig. 1.2 1000 900 potential difference /mV 800 700 600 500 current / μA (iii) Find the gradient of the line of best fit and hence calculate the lemon’s internal resistance, in ohms, Ω. Show your working. Internal resistance = ...................................................... Ω [3] (iv) A student suggests that two lemon cells in series could be used to run a 1.5V, 0.45W filament lamp. Explain why this is not correct.