A coaxial cable consists of a thin inner conductor fixed along the axis of a hollow outer conductor. The two conductor carry equal currents in opposite directions. Let `B_1 and B_2` be the magnetic fields in the region between the conductors and outside the conductor, respectively. Then,

Options

A. `B_(1)neB_(2)ne0`
B. `B_(1)=B_(2)=0`
C. `B_(1)neB_(2)=0`
D. `B_(1)=0,B_(2)ne0`

Answer

C

Explanation

Apply ampere's circular law to the coaxial circular loops `L_(1)` and `L_(2)`. The magnetic field is `B_(1)` at all points on `L_(1)` and `B_(2)` at all points on `L_(2). SigmaIne0` for `L_(1)` and `0` for `L_(2)`.

Hence `B_(1)ne0` but `B_(2)=0`
`[As oint vec(B).dvec(l)=mu_(0)SigmaI]`