# Questions on Characteristic Curves - Filament Lamp

Q5. When a filament lamp is switched on it takes 0.50 seconds for the filament to reach its normal operating temperature. The way in which the current changes during the first second after switching on is shown on the graph below.

(a) Use the graph to determine the maximum current through the lamp.

(1 mark)

(b) Assuming that the lamp is connected to a 12V dc supply of a negligible internal resistance,

(i) Calculate the resistance of the lamp when it has reached its normal operating temperature,

(1 mark)

(ii) Calculate the power of the lamp when it has reached its normal operating temperature.

(1 mark)

(c) Explain why the current through the lamp decreases between 0.05 s and 0.50 s.

(2 marks)

(d) State and explain the change, if any, to the final current through the lamp if it is connected to the same supply with another similar lamp

(i) in series,

(2 marks)

(ii) in parallel.

(2 marks)

(e) State and explain why a filament lamp is most likely to fail as it is switched on.

(2 marks)

(Total 11 marks)