1. 18.3 Resistance and Ohm’s law Resistance of a tungsten filamentExample 5 A student carried out an experiment to find the resistance of the tungsten filament of a bulb. He obtained the following results: Current through the filament I / A Voltage across the filament V / V 32.82.52.21.81.61.30.9 0 12108643210 (a) Plot a graph of V against I.

2. 18.3 Resistance and Ohm’s law 12 10 8 6 4 2 0 voltage / V 0.511.522.53 current / A

3. 18.3 Resistance and Ohm’s law No. The graph is a curve. Voltage is not directly proportional to the current. (b) (i) Find the resistance of the tungsten filament when the voltage is 4 V.  2.22  (b) (ii) Find the resistance of the tungsten filament when the voltage is 12 V.  4  (c) Does the tungsten filament obey Ohm’s law? Explain your answer.