Wires A and B, having equal lengths of 43.4 m and equal diameters of 2.71 mm, are connected in series. A potential difference of 61.2 V is applied between the ends of the composite wire. The resistances are RA = 0.127 02 and RB = 0.728 Q. For wire A, what are (a) magnitude J of the current density and (b) potential difference V? (c) Of what type material is wire A made (see the table below)? For wire B, what are (d) J and (e) V? (f) Of what type material is B made? Resistivities of Some Materials at Room Temperature (20C) Material Resistivity, p (n.m) Typical Metals Temperature Coefficient of Resistivity, a (K-) Silver 1.62 X 10-8 4.1 X 10-3 Copper 1.69 x 10-8 4.3 x 10-3 Gold 2.35 x 10-8 4.0 10-3 Aluminum 2.75 x 10-8 4.4 10-3 Manganin 4.82 10-8 Tungsten 5.25 x 10-8 0.002 x 10 4.5 10-3 Iron 9.68 10-8 6.5 x 10-3 Platinum 10.6 10-8 3.9 10-3 Typical Semiconductors Silicon, pure 2.5 x 103 -70 x 10-3 Silicon, n-type Silicon, p-type Glass Fused quartz 8.7 10-4 2.8 10-3 Typical Insulators 1010 1014 ~1016 "An alloy specifically designed to have a small value of a. "Pure silicon doped with phosphorus impurities to a charge carrier density of 1023 m. "Pure silicon doped with aluminum impurities to a charge carrier density of 1023 m.