IB Physics B.5-Paper 2-Qc#13-Power loss in 1 m of the cable

A cable consisting of many copper wires is used to transfer electrical energy from a generator to an electrical load. The copper wires are protected by an insulator. The copper wires and insulator are both exposed to an electric field. a. Discuss, with reference to charge carriers, why there is a significant
electric current only in the copper wires.
The cable consists of 32 copper wires each of length 35 km. Each wire has a
resistance of 64 Ω. The resistivity of copper is 1.7 x 10 Ω m.
b. Calculate the radius of each wire.
c. There is a current of 730 A in the cable. Show that the power loss in 1 m
of the cable is about 30 W.
d. When the current is switched on in the cable the initial rate of rise of
temperature of the cable is 35 mK/ s . The specific heat capacity of
copper is 390 J kg K . Determine the mass of a length of one metre of the cable.
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