Magnetic Effects Of Current Question 74

Question: A current I flows along the length of an infinitely long, straight and thin-walled pipe. Then [IIT-JEE 1993]

Options:

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

Show Answer

Answer:

Correct Answer: B

Solution:

Applying Ampere?s law $ \oint{B.dl={\mu_{0}}i} $ to any closed path inside the pipe we find no current is enclosed. Hence $ B=0. $