You have a piece of copper wire and a piece of carbon rod, each 1.5 m long and each having a cross-sectional area of 8.0 × 10−6 m2. When you connect the copper wire to the terminals of a 9.0-V battery, the current in the wire is I. Part A If you want to connect the carbon rod to another battery and have the same current I in the wire, what must the potential difference of the battery be? [ σcopper = 5.9 × 107 A/(V⋅m), σcarbon = 7.3 × 104 A/(V⋅m) ]