16   9 A student is planning to collect data to produce a current-potential difference graph for a filament lamp. Her teacher suggests two circuits that she could use. Circuit 1 Circuit 2 A V A V Circuit 1 uses a potential divider and circuit 2 uses a variable resistor to vary the potential difference across the filament lamp. *(a) Discuss the suitability of each circuit to collect the data. (6) .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. Turn over 17   (b) The student sets up the following circuit with the filament lamp. The battery has negligible internal resistance. 12 V 560 Ω A (i) The reading on the ammeter is 17.5 mA. Calculate the value of the potential difference (p.d.) across the filament lamp. (2) ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... ................................................................................................................................................................................................................................................... p.d. across filament lamp = ....................................................... (ii) When a voltmeter with a resistance of 1.5 kΩ is connected as shown, the p.d. across the filament lamp decreases. 12 V 560 Ω A V Explain why the p.d. across the filament lamp decreases. (3) .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. .................................................................................................................................................................................................................................................. (Total for Question 9 = 11 marks)