question_answer

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 from the axis is

A)            \[\infty \]                              

B)            Zero

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

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

Correct Answer: B

Solution :

                   The respective figure is shown below Magnetic field at P due to inner and outer conductors are equal and opposite. Hence net magnetic field at P will be zero.