In Fig. 5.1, sketch the $I$-$V$ characteristic of a filament lamp.
Explain how the lamp’s resistance can be calculated from its $I$-$V$ characteristic for any voltage.
First the two identical filament lamps are connected in series, and then they are connected in parallel, to a $12\ \text{V}$ power supply with negligible internal resistance. The two circuit diagrams are shown in Fig. 5.2 and Fig. 5.3 respectively.
State and explain why the resistance of each lamp in series is different from the resistance of each lamp in parallel.
Each lamp has the rating ‘$12\ \text{V},\ 50\ \text{W}$’. Calculate the total resistance of the circuit when the two lamps are arranged so that each lamp uses this power.
State and explain why the resistance of each lamp in series is different from the resistance of each lamp in parallel.
Each lamp has a rating of $12\text{V}, 50\text{W}$. Calculate the total resistance of the circuit for the two lamps connected so that each lamp uses this power.