Question

A current $i$ ampere flows along the inner conductor of a coaxial cable and returns along the outer conductor of the cable, then the magnetic induction at any point outside the conductor at a distance $r$ metre the axis is

• A. $\infty$
• B. Zero
• C. $\frac{{\mu }_0}{4\pi }\frac{2i}{r}$
• D. $\frac{{\mu }_0}{4\pi }\frac{2\pi i}{r}$

Answer 1

The correct option is B Zero

The described condition can be as shown in the above figure
The magnetic field at $P$ due to inner and outer conductors are equal and opposite. Hence, the net magnetic field at $P$ will be zero.