A current `i` flows along the length of an infinitely long, straight, thin-walled pipe. Then,
(a) the magnetic field at all points inside the pipe is the same, but not zero
(b) the magnetic field at any point inside the pipe is zero
(c) the magnetic field is zero only on the axis of the pipe
(d) the magnetic field is different at different points inside the pipe

Options

A. The magnetic field at all point inside the pipe is same, but not zero
B. The magnetic field at any point inside the pipe is zero
C. the magnetic field is zero only on the axis of the pipe
D. the magnetic field is different at different points inside the pipe

Answer

B

Explanation

(b) Using Ampere's circuital law, over a circular loop of any
radius less than the radius of the pipe, we can see that net
current inside the loop is zero. Hence, magnetic field at every
point inside the loop will be zero.