a 2.0-m length of wire is made by welding the end of a 120-cm-long silver wire to the end of an 80-cm-long copper wire. each piece of wire is 0.60 mm in diameter. the wire is at room temperature, so the resistivities are as given in table 25.1. a potential difference of 9.0 v is maintained between the ends of the 2.0-m composite wire.