State Ampere's law. A long solid conductor of radius a lies on the axis of a long cylinder of inner radius b and outer radius c. The central conductor carries a current i while the outer conductor carries a current -i . The currents are uniformly distributed over the cross-sections of each conductor. By considering the current enclosed by a circular loop of radius r centred on the axis of the inner conductor use Ampere's law to calculate the magnetic field in each of the four regions (a) r < a, (b) a < r < b, (c) b < r < c, (d) r > c.
Solution:
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