The student connects a single lamp $L_1$ to a power supply. The potential difference across the lamp is $V_1=6.0V$ and the current in the circuit is $I_1=0.50A$. Calculate the resistance $R_1$ of the lamp.

The student then connects three identical lamps $L_1$, $L_2$, and $L_3$ in series. The total potential difference across all three lamps is $V_3=6.0V$ and the current in the circuit is $I_3=0.25A$. Calculate the combined resistance $R_3$ of the three lamps connected in series.

A second student suggests that the combined resistance $R_3$ of the three identical lamps in series should be given by the equation $R_3=3\times R_1$. State whether the results from (a) and (b) agree with this suggestion. Justify your answer by comparing the values.

The student now wishes to connect the three lamps in parallel so that their behavior can be compared. Describe how to connect the components in a circuit consisting of a power supply, a switch, an ammeter, three lamps in parallel, a voltmeter to measure the potential difference across the lamps, and a variable resistor to control the total current in all three lamps.