电磁场与电磁波-作业答案.doc

Homework 1.Problem 4.7 A section of copper ring is shown in Figure P4.7. Find the resistance between the boundaries A and B. 2.Problem 4.8 A truncated circular cone, as illustrated in Figure P4.8, is made of iron. What is the resistance of the cone between its flat ends? 3.Problem 4.16 A solid conductor of radius 2mm and length 10 m is to be replaced with a hollow conductor of inner radius 2mm. If the two conductors are made of the same material and have the same length and resistance, what must be the outer radius of the hollow conductor? 4.Problem 4.10A copper wire of area 1cm2 carries a uniformly distributed current of 200A. If the electron density in copper is 8.5X1028 electrons per cubic meter, determine the average drift velocity of the electrons. What is the electric field intensity in the wire? If the wire is 100km long, calculate the potential difference between its ends. What is the resistance of the wire?