question_answer

Two identical circular current carrying coils 1 and 2, each of radius R are placed adjacently a distance d apart (d<<R). They carry equal currents/in opposite sense. Let \[{{L}_{1}},\,{{L}_{2}},\,{{M}_{12}}\] and\[{{M}_{21}}\] denote the self and mutual inductances. Which of the following is at least approximately true?

A) \[\left| \left. {{L}_{1}} \right| \right.=\left| \left. {{M}_{21}} \right| \right.\]

B) \[{{M}_{21}}>{{L}_{1}}\]

C) \[{{L}_{1}}=-{{L}_{2}}\]

D) \[{{M}_{12}}=-{{M}_{21}}\]