A coaxial cable carries the a current i in the inside conductor of radius a as shown in figure-4.80 and the outer conductor of inner radius b and outer radius c carries a current i' in opposite direction. Find the magnetic induction due to the coaxial cable at distance r from the central axis of the cable for (a) `r gt a`, (b) `a lt r lt b` and (c) `b gt r gt c`

Answer

[(a) `(mu_(0)i)/(2 pi n^(2))`; (b) `(mu_(0)i)/(2pir)`; (c) `(mu_(0))/(2 pir) [i - i' ((r^(2) - b^(2))/(c^(2) - b^(2)) ]`]