The magnetic moments associated with two closely wound circular coils $A$ and $B$ of radius $r_A = 10 \ cm$ and $r_B = 20 \ cm$ respectively are equal if: (Where $N_A, I_A$ and $N_B, I_B$ are the number of turns and current of $A$ and $B$ respectively)

  • A
    $2 N_A I_A = N_B I_B$
  • B
    $N_A = 2 N_B$
  • C
    $N_A I_A = 4 N_B I_B$
  • D
    $4 N_A I_A = N_B I_B$

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