A circular coil ‘$A$’ has a radius $R$ and the current flowing through it is $I$. Another circular coil ‘$B$’ has a radius $2R$ and if $2I$ is the current flowing through it, then the magnetic fields at the centre of the circular coil are in the ratio of (i.e.${B_A}$ to ${B_B}$)

  • [AIEEE 2002]
  • A

    $4:1$

  • B

    $2:1$

  • C

    $3:1$

  • D

    $1:1$

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