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Two coils of self inductance *L*_{1} and *L*_{2} are placed closer to each other so that total flux in one coil is completely linked with other. If *M* is mutual inductance between them, then

(1) *M* = *L*_{1}* L*_{2}

(2) *M* = *L*_{1}/*L*_{2}

(3) $M=\sqrt{{L}_{1}{L}_{2}}$

(4) *M* = (*L*_{1}* L*_{2})^{2 }