Correct Option(b) zero
Explanation:
Let R be the radius of a long thin cylindrical shell.
To calculate the magnetic induction at a distance r, (r <R) from the axis of the cylinder, a circular shell of radius r is shown.
Since, no current is enclosed in the circle, so from Ampere's circuital law. magnetic induction is zero at every point of the circle. Hence, the magnetic induction at very point inside the infinitely long straight thin-walled tube (cylindrical) is zero.
