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.
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correct curve in positive quadrant 
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correct curve in negative quadrant
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passing through origin
(3)
(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
pd. and current do not increase proportionally .
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
(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.
Circuit diagram marks:
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battery, variable resistance (or variable supply) and filament
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current sensor in series circuit
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voltage sensor across filament
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the two sensor boxes connected to datalogger
Method marks:
The variable resistor or variable supply voltage is altered for each reading
thus changing both V and I
(5 max)
(Total 11 marks)
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