A filament lamp rated 15 V, 1.0 A has a resistance of 3.0 Ω when it carries no current.
Figure 1
On the axes in Figure 1, sketch the form of the current against voltage characteristic for this lamp.
Explain why, as the voltage is increased either positively or negatively from zero, the characteristic has the form shown in your answer for part (a).
Using your answer from part (b), explain, in terms of electron flow how the resistance of the filament lamp changes as the current in the lamp increases.
Figure 2 shows part the current-voltage (I-V) characteristic of a lamp up to its working voltage.
Figure 2
Calculate the resistance in the lamp when 0.5 A of current is passed through it.
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