Two resistors, A and B, are connected in series in a closed loop that also contains a single ideal battery. A student measures the electric potential along the loop and constructs the following description of the graph:
• Over the length of resistor A (0.30 m), the potential decreases uniformly from 12 V to 3 V.
• Over the length of resistor B (0.10 m), the potential decreases uniformly from 3 V to 0 V.
Both resistors are made from the same material but may have different cross-sectional areas AA and AB. Conventional current is the same through both resistors.
Which of the following best gives the ratio AB/AA?
a) 31
b) 3
c) 1
d) 9