A long, straight, hollow conductor (tube) carrying a current has two sections A and C of unequal cross sections joined by a conical section B. 1,2 and 3 are points on a line parallel to the axis of the conductor. The magnetic fields at 1,2 and 3 have magnitudes `B_1, B_2 and B_3`. Then,

Options

A. `B_(1)=B_(2)=B_(3)`
B. `B_(1)=B_(2)neB_(3)`
C. `B_(1) lt B_(2) lt B_(3)`
D. `B_(2)` cannot be found unless the dimensions of the section `B` are known

Answer

A

Explanation

To find the magnetic field outside a thick conductor, the current may be assumed to flow along the axis. As point `1,2,3` are equidistance from the axis.
`B_(1)=B_(2)=B_(3)`