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. $\frac{\mu_{o}}{4\pi} \frac{2i}{r}$ tesla
• D. $\frac{2i}{r}$ tesla

Answer 1

Answer: (B)

zero

Answer 2

Considering Ampere?s loop (shown by dotted line), no current is enclosed by this loop. Therefore, the magnetic field will be zero inside the tube.