Question

Two coils of self inductance $2mH$ and $8mH$ are placed so close together that the effective flux in one coil is completely linked with the other. The mutual inductance between these coils is

• A. $16mH$
• B. $10mH$
• C. $6mH$
• D. $4mH$

Answer 1

Answer: (D)

Mutual inductance between coils is
$\text{M} = \text{K} \sqrt{\text{L}_{1} \text{L}_{2}}$
or, $\text{M} = 1 \sqrt{2 \times 1 0^{- 3} \times 8 \times 1 0^{- 3}}$ $\left(\because \text{K} = 1\right)$
$= 4 \times 1 0^{- 3} = 4 \text{ mH}$