Questions on Characteristic Curves - Filament Lamp
Q3.
(a) Draw, on the axes below, the current/voltage characteristic for a filament lamp.
Do not insert any values for current or voltage.
![](Q3a.png)
(3 marks)
(b) Explain why the characteristic has the shape you have drawn.
The current heats the filament
making the temperature rise.
Resistance of a wire increases with temperature
but
p.d. and current do not increase proportionally. ![](../../../../graphics/symbols/nuclides/ticksmall.png)
It does not matter which way round you connect a filament lamp in a circuit therefore current passing through it in the opposite direction has the same effect - producing the same shape of characteristic in the negative quadrant. ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(Max 3)
(c) The current/voltage characteristic of a filament lamp is to be determined using a datalogger, the data then being fed into a computer to give a visual display of the characteristic. Draw the circuit diagram required for such an experiment and state what is varied so as to produce a range of values.
![](../../../../graphics/diagrams/electricity/data_logger_Q2.png)
Circuit diagram marks:
battery, variable resistance (or variable supply) and filament
current sensor in series circuit
voltage sensor across filament
the two sensor boxes connected to datalogger ![](../../../../graphics/symbols/nuclides/ticksmall.png)
Method marks:
The variable resistor or variable supply voltage is altered for each reading ![](../../../../graphics/symbols/nuclides/ticksmall.png)
thus changing both V and I ![](../../../../graphics/symbols/nuclides/ticksmall.png)
(5 max)
(Total 11 marks)