A light bulb and a resistor are connected in series to a variable power supply. A student first connects a voltmeter and an ammeter to measure the current through and the voltage across the bulb, as shown in the left circuit. The student varies the power supply voltage and records the readings on the meters.
The student then places the voltmeter across the resistor as shown in the right circuit, and repeats the experiment. She plots the data for both circuit elements in a single graph, as shown below.
a)Suppose the power supply voltage is now set to +3.0 V. For this power supply voltage, is the absolute value of the voltage across the bulb greater than, less than, or equal to 3.0 V?
b)Use the graph to estimate the current through the bulb when the power supply voltage is +3.0 V.
The Attempt at a Solution
a) The two elements are in series, so I believe the voltage across the bulb would have to be less than 3V
b) I'm having trouble with this since the resistance of the bulb is varying.