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.

    • correct curve in positive quadrant
    • correct curve in negative quadrant
    • 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:
    • battery, variable resistance (or variable supply) and filament
    • current sensor in series circuit
    • voltage sensor across filament
    • 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)