Complete the circuit diagram with suitable circuit symbols for the lamp, a voltmeter and a variable resistor.
The ammeter used by the student has ranges 0-10 A, 0-1 A, 0-100 mA and 0-10 mA. Describe how the student should use the different ranges to obtain readings that let all nine points be plotted accurately on the graph while keeping the ammeter safe.
State how Fig. 9.1 shows that the lamp does not obey Ohm’s law.
Using Fig. 9.1, determine the resistance of the lamp when the voltmeter reading is 0.40 V.
Using Fig. 9.1, determine the resistance of the lamp when the voltmeter reading is 6.0 V.
Explain why the resistance of the lamp changes as the voltage changes.
State how a wire’s resistance depends on its length and how it depends on its cross-sectional area. length cross-sectional area
The student gets a long piece of wire made from the same material as the filament in the lamp. The wire he gets has the same cross-sectional area as the filament. He cuts a 1.0 m length of the wire and measures its resistance at room temperature. He obtains the value $16\,\Omega$. Using the suitable resistance value from (d), estimate the length of the filament wire in the lamp.