A 3.00-m length of copper wire at 20° C has a 1.20-m-long section with diameter 1.60 mm...

A 3.00-m length of copper wire at 20° C has a 1.20-m-long section with diameter 1.60 mm and a 1.80-m-long section with diameter 0.80 mm. There is a current of 2.5 mA in the 1.60- mm-diameter section. (a) What is the current in the 0.80-mm-diameter section? (b) What is the magnitude of in the 1.60-mm-diameter section? (c) What is the magnitude of in the 0.80-mm-diameter section? (d) What is the potential difference between the ends of the 3.00-m length of wire?