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!=0, B_2!=0`
B. `B_1=B_2=0`
C. `B_1!=0, B_2=0`
D. `B_1=0, B_2!=0`

Answer

C

Explanation

(c) Apply Ampere's circuital 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. SigmaI!=0` for `L_1` and 0 for `L_2`.
Hence, `B_1!=0 but B_2=0`
[As `oint vecB.dvecl=mu_0 sumI`]