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!=B_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

(a) To find the magnetic field outside a thick conductor, the
current may be assumed to flow along the axis. As point 1,
2 and 3 are equidistant form the
axis
`B_1=B_2=B_3`