# Questions on Characteristic Curves - Filament Lamp

Q6.

(a) Sketch, on the axes below, the currentâ€“voltage (IV) characteristic for a filament lamp for currents up to its working power.

[2 marks]

(b)

(i) State what happens to the resistance of the filament lamp as the current increases.

[1 mark]

(ii) State and explain whether a filament lamp is an ohmic or non-ohmic conductor up to its working power.

[1 mark]

(c) Three identical filament lamps, P, Q and R are connected in the circuit as shown below:

The filament in lamp Q melts so that it no longer conducts. Explain why lamp P becomes brighter and lamp R becomes dimmer.

[2 marks]

(d) A filament lamp, X, is rated at 60 W 230 V.

Another type of lamp, Y, described as 'energy saving' has the same light intensity output but is rated at 11 W 230 V.

(i) Calculate the electrical energy converted by each lamp if both are on for 4 hours a day for a period of 30 days.

[2 marks]

(ii) Suggest why the two lamps can have different power ratings but have the same light intensity output.

[2 marks]

(Total 10 marks)