A copper wire has radius r = 0.0250 cm, is 3.00 m long , has resistivity= 1.72x10^-8
and carriers a current of 0.400 A. the wire has a charge-carries density of 8.50x10^28 electrons/m^3.
a) what is the resistance ,R, of the wire?
b)what is the electric potential difference ,across the wire?
c)what is the electric field E,in the wire?