Consider a long straight wire of a circular cross-section (radius $a$) carrying a steady current $I$. The current is uniformly distributed across this cross-section. The distances from the centre of the wire's cross-section at which the magnetic field [inside the wire,outside the wire] is half of the maximum possible magnetic field,anywhere due to the wire,will be

  • A
    $[a/4, 3a/2]$
  • B
    $[a/2, 2a]$
  • C
    $[a/2, 3a]$
  • D
    $[a/4, 2a]$

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