Questions on Characteristic Curves - Filament Lamp


In an attempt to investigate how the resistance of a filament lamp varies with current through the lamp, a student obtains the results shown in the table below:


voltage /V 0.50 1.50 3.00 4.50 6.00 12.00
current /A 0.51 1.25 2.00 2.55 2.95 4.00
resistance /            


(a) Complete the table by calculating the corresponding values of resistance.

(2 marks)


(i) On an A4 sheet of graph paper plot a graph of resistance against current for the filament lamp.

(ii) Use your graph to estimate the resistance of the filament lamp when no current flows through the lamp.

(iii) Use your graph to determine the change in the resistance of the filament when the current increases:

from 0 to 1.0 A,

from 1.0 A to 2.0 A

(iv) Calculate the power dissipated in the lamp filament when the current through the filament is 1.0 A and 2.0 A.

(8 marks)

(c) Using information from part (b)(iv), explain why the change in resistance of the filament is less for a current change of 0 to 1.0 A than for a current change of 1.0 A to 2.0 A. Do not attempt any calculation.

(2 marks)

(Total 12 marks)