to investigate the variation of current(i) with pd(v) for a filament bulb

Question 1

describe how the student varied the potential difference.

Answer 1

a rheostat or variable resistor. by adjusting the rheostat, the resistance of the circuit is adjusted. the voltage is being divided between the thin metallic conductor’s resistance and the rheostat’s resistance, and when adjusted or varied, results to lowering/increasing the voltage

Question 2

what does your graph tell you about the variation of current with potential difference for a filament lamp?

Answer 2

the graph is a straight-line through the origin showing that for a filament bulb at constant temperature, the current is directly proportional to the applied voltage-until the high current produces a heating effect which makes the graph taper off as the resistance increases.

Question 3

give a reason why the resistance of the filament bulb changes.

Answer 3

due to the heating effect of an electric current. at high current, the temperature of the filament increases. this means the same change in potential difference does not cause as large an increase in current, as the resistance increases.