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$\frac{{{\mu _0}}}{{4\pi }}\frac{{2\pi \,i}}{r}$
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