The following data were obtained for a small torch bulb when different cells were connected across it:
Potential difference V (V): 1.5, 3.0, 4.5
Current I (A): 0.30, 0.55, 0.75
(i) Compute the electrical power corresponding to each operating point.
(ii) Plot a graph of power (y-axis) versus potential difference (x-axis) and describe the trend you observe.
(iii) Determine the resistance of the bulb at 1.5 V and at 4.5 V. Comment on the change in resistance with increasing voltage and offer a physical reason for this behaviour.