question_answer

A current of i ampere flows along an infinitely long straight thin walled tube, then the magnetic induction at any point inside the tube at a distance r from the centre is:

A)  Infinite           

B)  zero

C)  \[\frac{{{\mu }_{0}}}{4\pi }.\,\frac{2i}{r}\]

D)  \[\frac{2i}{r}\].0

Correct Answer: B

Solution :

No current is enclosed in the circle of radius r, so from Amperes circuital law, the magnetic induction at any point inside the infinitely long straight thin walled tube (cylindrical) is zero.