Question

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 B₁, B₂ and B₃ respectively, then:

• A. B₁ = B₂ = B₃
• B. B₁ = B₂¹ B₃
• C. B₁< B₂< B₃
• D. B₂ cannot be found unless the dimensions of the section B are known

Answer 1

Answer: (A)

B₁ = B₂ = B₃

Answer 2

To find the magnetic field outside a thick conductor, the current may be assumed to flow along the axis. As points 1 , 2 , 3 are equidistant from the axis, B₁ = B₂ = B₃