A long, thin, hollow cylindrical tube of radius r carries a current i along its length. Determine the magnitude of the magnetic field at a distance r/2 from the surface, inside the tube.

Step-by-step solution

Using Ampere's circuital law: B d l = ₀ I_ enclosed For a point inside the hollow cylindrical tube at a distance r/2 from the surface, the distance from the axis is r - r/2 = r/2 . An Amperian loop of radius r/2 inside the hollow tube encloses no current, so I_ enclosed = 0 . Therefore, B 2 ( r 2 ) = 0 B = 0 The magnetic field at any point inside the hollow tube is zero.