Question

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

• A. infinite
• B. zero
• C. $\frac{{\mu }_0}{4\pi }.\frac{2i}{r}$ tesla
• D. $\frac{2i}{r}$ tesla

Answer 1

Answer: (B)

zero

Since what is being considered is a thin-walled tube, there is current flowing only on the surface of the tube. If we draw any circuital loop inside the wire, it does not enclose any current. Hence, according to Ampere's Circuital Law, there is no induced magnetic field inside.